ganex iii-n newsletter - knowmade

Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)

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GANEX

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GANEX Newsletter No. 77 June 2019

III-N Technology

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GaNEX | III-N Technology Newsletter No. 77 | 2

METHODOLOGY

Each month

150+ new scientific publications

200+ new patent applications

30+ new press releases

Sources 10+ scientific journal editors

Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …

10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,

Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …

Patent database: Questel-Orbit

Selection by III-N French

experts

GANEX monthly newsletter


TABLE OF CONTENTS (clickable links to chapters)

SCIENTIFIC PUBLICATIONS ............................................................................................................................. 4

GROUP 1 - LEDs and Lighting ................................................................................................................................. 4

GROUP 2 - Laser and Coherent Light ..................................................................................................................... 9

GROUP 3 - Power Electronics .............................................................................................................................. 12

GROUP 4 - Advanced Electronics and RF ............................................................................................................. 16

GROUP 5 – MEMS and Sensors............................................................................................................................ 22

GROUP 6 - Photovoltaics and Energy harvesting................................................................................................. 27

GROUP 7 - Materials, Technology and Fundamental .......................................................................................... 32

PRESS RELEASE ............................................................................................................................................ 46

PATENT APPLICATIONS ................................................................................................................................ 72


SCIENTIFIC PUBLICATIONS Selection of new scientific articles

GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)

Information selected by Mathieu Leroux (CRHEA-CNRS)

Highly polarized photoluminescence from c-plane

InGaN/GaN multiple quantum wells on stripe-

shaped cavity-engineered sapphire substrate Department of Materials Science and Engineering, Seoul

National University, Seoul, 08826, Korea

Department of Electronics Engineering, Catholic University

of Daegu, Gyeongbuk, 38430, Korea

Research Institute of Advanced Materials, Seoul National

University, Seoul, 08826, Korea

Inter-university Semiconductor Research Center, Seoul

National University, Seoul, 08826, Korea

Scientific Reports

https://doi.org/10.1038/s41598-019-44519-2

Highly polarized photoluminescence (PL) from c-

plane InGaN/GaN multiple quantum wells (MQWs)

grown on stripe-shaped cavity-engineered sapphire

substrate (SCES) was realized. The polarization ratio

was as high as 0.74 at room temperature. High-

resolution X-ray reciprocal space mapping

measurements revealed that the InGaN quantum

wells on GaN/SCES template were under

considerable anisotropic in-plane strain states of

−1.178% and −1.921% along the directions

perpendicular and parallel to the stripe-pattern,

respectively. The anisotropic strain states were

attributed to the anisotropic alignment of cavity-

incorporated sapphire nano-membranes, which

accommodated both anisotropic elastic relaxation in

the InGaN quantum well plane as well as the graded

elastic relaxation along the vertical direction in the

GaN template adjacent to the InGaN/GaN MQWs.

The partial strain relaxation in the InGaN wells also

contributed to reduction of quantum confined Stark

effect, resulting in four times higher PL intensity than

InGaN/GaN MQWs on planar sapphire substrate.

From theoretical calculations based on k∙p

perturbation theory, it was found that fundamental

origin of the polarized optical emission was strain-

induced modification of valence band structures of

the InGaN/GaN MQWs on the SCES. This study will

allow us to realize light emitting diodes with highly

polarized emission with conventional c-plane

sapphire substrates by strain-induced valence band

modification.

Correlation of Optical, Structural and Compositional

Properties with V-Pit Distribution in InGaN/GaN

Multi-Quantum Wells IHP- Leibniz-Institut für innovative Mikroelektronik, Im

Technologiepark 25, 15236 Frankfurt (Oder), Germany.

European Synchrotron Radiation Facility, BP 220, 38043

Grenoble Cedex, France.

Université Grenoble Alpes, CNRS, Grenoble INP, SIMAP,

38000 Grenoble, France.

OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055

Regensburg, Germany.

Department of Microsystems Engineering (IMTEK),

University of Freiburg, Georges-Köhler-Allee 103, 79110

Freiburg, Germany.

Institute of Physics, Technische Universität Chemnitz,

Reichenhainer Straße 70, 09126 Chemnitz, Germany.

Leibniz-Institut für Kristallzüchtung (IKZ), Max-Born Str.2,

12489 Berlin, Germany.

ACS Appl. Mater. Interfaces

https://doi.org/10.1021/acsami.9b04431

InGaN/GaN double heterostructures and multi-

quantum wells have been successfully developed

since more than 20 years for LED lightning

applications. Recent developments show that state-

of-the-art LEDs benefit from artificially generated V-

pit defects. However, the control of structural and

chemical properties plays a tremendous role. In this

paper we report on the lateral distribution of V-pit

defects and photoluminescence of InGaN/GaN multi

quantum wells grown on thick GaN on patterned

sapphire substrates. The synchrotron based scanning

x-ray diffraction microscopy technique K-Map was

employed to locally correlate these properties with

the local tilt, strain and composition of the

InGaN/GaN multi-quantum well. Compositional

fluctuation is the main factor for the variation of

https://doi.org/10.1038/s41598-019-44519-2



photoluminescence intensity and broadening. In turn

V-pit defects, align along small-angle grain

boundaries, and their strain fields are identified as

reason for promoting the InGaN segregation process

on a microscale.

Effect of electron blocking layer on the efficiency of

AlGaN mid-ultraviolet light emitting diodes Department of Electrical Engineering and Computer

Science, University of Michigan, 1301 Beal Avenue, Ann

Arbor, Michigan, MI 48109, USA

Department of Electrical and Computer Engineering,

McGill University, 3480 University Street, Montreal,

Quebec H3A 0E9, Canada

Optics Express

https://doi.org/10.1364/OE.27.00A738

The performance of AlGaN-based mid and deep

ultraviolet light emitting diodes (LEDs) is severely

limited by electron overflow and by the poor hole

injection into the device active region. We have

studied the effect of various electron blocking layers

on the performance of AlGaN LEDs operating at ~280

nm. It is observed that, compared to conventional p-

type electron blocking layer, the incorporation of an

n-type AlN/AlGaN superlattice electron blocking layer

before the active region can significantly improve the

device performance by reducing electron overflow

without compromising hole injection. Direct on-wafer

measurement showed an external quantum

efficiency ~4.4% and wall-plug efficiency ~2.8% by

optimizing the design of n-type AlN/AlGaN

superlattice electron blocking layer, which is nearly a

factor of five to ten times better than identical

devices but with the incorporation of a conventional

p-type electron blocking layer.

Influence of LO and LA phonon processes on

thermal-nonequilibrium excitation and deexcitation

dynamics of excitons in GaN, AlN, and ZnO Department of Electrical and Electronic Engineering, Chiba

University, 1-33 Yayoicho, Inage-ku, Chiba 263-8522, Japan

Journal of Applied Physics

https://doi.org/10.1063/1.5092620

The 1S-exciton density NX(1) in GaN, AlN, and ZnO is

calculated for thermal-nonequilibrium states where

the temperatures of an electron–hole system and

phonons are different in the range of 10–400 K. The

ratio of NX(1) in AlN to that in ZnO reaches 21 despite

the similar exciton-binding energies of AlN and ZnO,

which is due to the higher rate of excitation by LO-

phonon absorption in ZnO. This result reveals that

thermal-nonequilibrium states significantly affect the

validity of evaluation methods for physical

parameters such as internal quantum efficiency of

radiation. The ratio of NX(1) in AlN to that in ZnO is

enhanced from 2.2 to 18 by the occupation of states

of the principal quantum number n from 2 to 5. This

result demonstrates the importance of the discussion

on the n≥3 states which have not been taken into

account in other analyses. The main reason for the

decrease in NX(1) is found to be the increase in the

temperature of LO phonons rather than LA phonons,

which indicates the importance of LO-phonon control

in light-emitting devices. The results for general

thermal-nonequilibrium states are nontrivial because

the mechanisms of the population balance are

complicated owing to the several-n occupation and

the transition rates determined by various factors.

Our analyses and discussions quantitatively unveil the

LO- and LA-phonon effects on the thermal-

nonequilibrium excitation and deexcitation dynamics

of excitons and provide the basis for design of highly

efficient light-emitting devices particularly in the

ultraviolet region.

Modification of strain and optical polarization

property in AlGaN multiple quantum wells by

introducing ultrathin AlN layer Engineering Research Center of Micro-nano Optoelectronic

Materials and Devices, Ministry of Education; Fujian Key

Laboratory of Semiconductor Materials and Applications,

CI Center for OSED, Jiujiang Res Inst and Department of

Physics, Xiamen University, Xiamen 361005, China

AIP Advances

https://doi.org/10.1063/1.5091027

The effects of ultrathin AlN insertion layers on the

strain status, as well as optical properties of AlGaN

multiple quantum wells (MQWs), were studied. A

large stress variation of about -1.46 GPa can be

achieved by introducing two ultrathin AlN layers at

each interface between the quantum well and the

barrier, thereby resulting in the fact that the degree

https://doi.org/10.1364/OE.27.00A738

https://doi.org/10.1063/1.5092620

https://doi.org/10.1063/1.5091027


of polarization is increased from 17.8% to 22.3% in

traditional MQWs. In addition, the quantum well

emission are found to become symmetric and

narrower due to the suppression of compositional

fluctuation. These results provide a simple technique

to modify the strain field of MQWs so as to improve

transverse-electric polarized emission for deep

ultraviolet light emitting diodes.

Polarization control in nitride quantum well light

emitters enabled by bottom tunnel-junctions Department of Electrical and Computer Engineering,

Cornell University, Ithaca, New York 14853, USA

Institute of High Pressure Physics, Polish Academy of

Sciences, Sokołowska 29/37, PL-01-142 Warsaw, Poland

Department of Materials Science and Engineering, Cornell

University, Ithaca, New York 14853, USA

Kavli Institute for Nanoscale Science, Cornell University,

Ithaca, New York 14853, USA


https://doi.org/10.1063/1.5088041

The frozen internal polarization-induced electric

fields due to broken inversion symmetry in all

conventional blue and green nitride semiconductor

light-emitting semiconductor quantum well

heterostructures point in a direction opposite to

what is desired for efficient flow of electrons and

holes. This state of affairs has persisted because of

the desire to have p-type hole injectors on top of the

quantum well active region. Because of the internal

polarization fields in nitride heterostructures, there

exist four permutations of doping and polarization for

the realization of such light emitters. Which

permutation is the most desirable for efficient light

emission? In this work, we answer this question by

demonstrating a fundamentally new approach

toward efficient light emission with “bottom-tunnel

junctions.” The bottom-tunnel junction design aligns

the polarization fields in the desired direction in the

quantum well while simultaneously eliminating the

need for p-type contacts and allowing efficient

current spreading. By preventing electron overshoot

past quantum wells, it disables carrier recombination

in undesired regions of the quantized

heterostructures and opens up the possibility for new

geometries of integrating and stacking multiple light

emitters.

Enhanced Performance of InGaN‐Based Blue LEDs

Using an AlGaN/InGaN Super‐Lattice Last Quantum

Barrier Wuhan National Laboratory for Optoelectronics, Huazhong

University of Science and Technology, Wuhan 430074,

China

physica status solidi a

https://doi.org/10.1002/pssa.201800913

In this work, a novel structure of InGaN‐based blue

light‐emitting diodes (LEDs) using a super‐lattice

structure as the last quantum barrier (QB) in the

active region is proposed to improve the blue LEDs

performance. The optical power and external

quantum efficiency (EQE) are investigated by both

simulation and experiment. The proposed

super‐lattice last QB can significantly enhance the

effective barrier of electrons from 463 to 576 meV in

the conduction band and thus block the leakage of

electrons. It is found that such structure can also

facilitate the hole injection due to the reduced

effective barrier height from 293 to 261 meV in the

valance band. Eventually, the increase of the carrier

concentration in the active region further improves

the internal quantum efficiency (IQE) of the device.

The experimental results indicate that the output

power of the proposed LED is increased by 16.9%

compared with the conventional LED, with lower

efficiency droop (less than 20.65%). The proposed

structure can be an alternative in pursuing high

efficiency blue LEDs in the future.

Growth and characterization of InxGa1−xN

(0 < x < 0.16) templates for controlled emissions

from MQW Department of Electrical and Computer Engineering, North

Carolina State University, Raleigh, NC 27695, USA

Department of Materials Science and Engineering, North

Carolina State University, Raleigh, NC 27695, USA

Journal of Crystal Growth

https://doi.org/10.1016/j.jcrysgro.2019.05.019

InxGa1−xN (0 < x < 0.16) templates were grown by

Metal Organic Chemical Vapor Deposition (MOCVD)

using the semibulk (SB) growth approach. We have

studied the impact of different SB design parameters

such as the number of (InGaN/GaN) periods, InGaN

https://doi.org/10.1063/1.5088041




layer thickness (T), and the GaN substrate quality on

the SB-template properties, and its degree of

relaxation. SIMS characterization measured the

variation of indium content (x) in the template, while

photoluminescence reflected the indium content at

the topmost layers of the SB template. X-ray

diffraction techniques measured the average lattice

parameters and degree of strain relaxation through

the entire InxGa1−xN SB-templates. The SB approach

results in superior material quality relative to the bulk

grown InGaN, mainly due to its ability to avoid the

inclusion of indium-rich clusters and V-pits in the SB

templates. The SB approach slows down the

relaxation processes and templates as thick as

750 nm are not fully relaxed. We are reporting on

methods to enhance the relaxation processes in

InxGa1−xN SB-templates. Finally, when InxGa1−xN

templates with 0 ≤ x ≤ 0.16 are used as substrates for

InGaN/GaN multiple quantum wells, the emission

wavelength is shifted from blue to green by changing

the indium content in the InxGa1−xN SB-templates.

To the best of our knowledge, the current results

present the highest indium content reported in

InxGa1−xN SB-templates.

Recent progress of tunnel junction-based ultra-

violet light emitting diodes Department of Electrical and Computer Engineering, The

Ohio State University, Columbus, Ohio, 43210, United

States of America

Department of Materials Science and Engineering, The

Ohio State University, Columbus, Ohio, 43210, United

States of America

Japanese Journal of Applied Physics

https://doi.org/10.7567/1347-4065/ab1254

AlGaN-based UV LEDs are promising for a wide range

of industrial, household and healthcare applications.

However, widespread adoption of UV LEDs is limited

by the poor device efficiency. This has been

attributed to the strong internal light absorption and

poor electrical injection efficiency associated with the

conventional UV LED structures, which typically use

an absorbing p-GaN layer for p-type contact. Recent

development of ultra-wide bandgap AlGaN tunnel

junctions enabled a novel UV LED design with the

absence of the absorbing p-GaN contact layer. In this

work, we review the recent progress of AlGaN tunnel

junctions and the development of tunnel junction-

based UV LEDs, and discuss the challenges and future

perspectives for the realization of high power, high

efficiency UV LEDs.

The polarization field in Al-rich AlGaN multiple

quantum wells Department of Materials Science and Engineering, North

Carolina State University, Raleigh, NC 27695, United States

of America

Adroit Materials, 2054 Kildaire Farm Rd, Suite 205, Cary,

NC 27518, United States of America


https://doi.org/10.7567/1347-4065/ab07a9

This paper investigates the quantum confined Stark

effect in AlGaN multiple quantum well structures

with a high Al content grown on single-crystalline AlN

substrates. The quantitative relationship between the

quantum well structure parameters, photogenerated

carrier density, built-in electric field and ground-level

emission is discussed. It is found that the electric field

strength increases from 0.5 MV cm−1 to almost 3 MV

cm−1 when the Al content in the quantum well

barriers is increased from 65% to 100%, which is

consistent with the theory of spontaneous and

piezoelectric polarization in III-nitrides. In addition,

the built-in electric field increases significantly with

increasing barrier thickness. Based on these results,

the electric field in an Al0.55Ga0.45N single quantum

well with AlN cladding is predicted to be around 5 MV

cm−1.

Study of AlN based materials grown on nano-

patterned sapphire substrates for deep ultraviolet

LED applications Advanced Micro-Fabrication Equipment Inc., 188 Taihua

Road, Shanghai, People's Republic of China


https://doi.org/10.7567/1347-4065/ab09de

High quality and crack-free AlN films were obtained

by using nano-patterned sapphire substrates (NPSS)

grown at AMEC Prismo HiT3TM MOCVD platform. It

is believed that the introduced epitaxial lateral

overgrowth can annihilate most of dislocations and

the grain boundary induced tensile stress can be

https://doi.org/10.7567/1347-4065/ab1254

https://doi.org/10.7567/1347-4065/ab07a9

https://doi.org/10.7567/1347-4065/ab09de


significantly suppressed by NPSS. For a 5 μm thick AlN

film, FWHMs of 173 arcsec and 335 arcsec were

observed from AlN (002) and (102) X-ray rocking

curves, respectively, indicating the high crystalline

quality. The surface of AlN films grown on NPSS

shows a typical step-bunching morphology with

atomic steps on the bunched terrace. In addition, we

also obtained excellent thickness uniformity for AlN

films grown on NPSS with within-wafer and wafer-to-

wafer thickness uniformity of 0.69% and 0.92%,

respectively.

Enhanced Wall-Plug Efficiency in AlGaN-Based Deep-

Ultraviolet LED via a Novel Honeycomb Hole-Shaped

Structure Wuhan National Laboratory for Optoelectronics, Huazhong

University of Science and Technology, Wuhan 430074,

China

State Key Laboratory of Infrared Physics, Shanghai Institute

of Technical Physics, Chinese Academy of Sciences,

Shanghai 200083, China.

IEEE Transactions on Electron Devices

https://doi.org/10.1109/TED.2019.2913962

The novel honeycomb hole-shaped electrode (HHSE)

structure was proposed for 280-nm AlGaN-based flip-

chip deep-ultraviolet light emitting diode (DUV-LED),

which was demonstrated to be beneficial to the

current spreading, optical emission, and heat

dispersion. By means of the finite element method,

we investigated the current density distribution at an

injection current density of 67.5 A/cm² and found

that the effective current spreading area was

approximately improved by 35.3% for the light

emitting diode (LED) with a novel electrode

compared with the LED with the conventional finger-

shape electrode. As a result, the wall-plug efficiency

(WPE) of the LED with a novel electrode was

increased by 28% at an injection current of 280 mA.

Meanwhile, the symmetrical distribution of optical

emission and temperature was realized. This paper

paves the way to solve the current crowding effect

due to the poor conductivity of the n-AlGaN layers

with high Al fraction and significantly develop high

efficiency in the AlGaN-based DUV-LED.

Effects of Meshed p-type Contact Structure on the

Light Extraction Effect for Deep Ultraviolet Flip-Chip

Light-Emitting Diodes Key Laboratory of Electronic Materials and Devices of

Tianjin, School of Electronics and Information Engineering,

Hebei University of Technology, Tianjin, People’s Republic

of China

Nanoscale Research Letters

https://doi.org/10.1186/s11671-019-2984-0

In this work, flip-chip AlGaN-based deep ultraviolet

light-emitting diodes (DUV LEDs) with various

meshed contact structures are systematically

investigated via three-dimensional finite-difference

time-domain (3D FDTD) method. It is observed that

both transverse electric (TE)- and transverse

magnetic (TM)-polarized light extraction efficiencies

(LEEs) are sensitive to the spacing and inclined angle

for the meshed structure. We also find that the LEE

will not be increased when a large filling factor is

adopted for the meshed structures, which is because

of the competition among the p-GaN layer

absorption, the Al metal plasmon resonant

absorption, and the scattering effect by meshed

structures. The very strong scattering effect occurring

in the hybrid p-GaN nanorod/p-AlGaN truncated

nanocone contacts can enormously enhance the LEE

for both TE- and TM-polarized light, e.g., when the

inclined angle is 30°, the LEE for the TE- and TM-

polarized light can be increased by ~ 5 times and ~ 24

times at the emission wavelength of 280 nm,

respectively.

https://doi.org/10.1109/TED.2019.2913962

https://doi.org/10.1186/s11671-019-2984-0


GROUP 2 - Laser and Coherent Light Group leader: Bruno Gayral (CEA)

Information selected by Knowmade

Analysis of optical injection on red and blue laser

diodes for high bit-rate visible light communication Optoelectronics Research Laboratory, Electrical

Engineering Department, King Fahd University of

Petroleum & Minerals, Dhahran 31261, Saudi Arabia

Photonics Laboratory, Computer, Electrical and

Mathematical Sciences and Engineering (CEMSE) division,

King Abdullah University of Science & Technology (KAUST),

Thuwal 23955-6900, Saudi Arabia

Optics Communications

https://doi.org/10.1016/j.optcom.2019.05.034

In this work, self-injection and external-injection in

450 nm InGaN/GaN blue and 650 nm InGaP/AlGaInP

red diode lasers are investigated. A distinct locking

characteristic is observed in the self-injection case

with small 19 cm cavity length, demonstrating

enhanced 2.34 and 2.07 GHz 3-dB bandwidths,

corresponding to a factor of 1.4 and 1.1

improvement, and reduced 60 and 80 pm spectral

linewidths, for the blue and the red lasers,

respectively. Moreover, this short external cavity self-

injection locked system exhibited superior

performance by a factor of 1.1–1.3 compared to the

long cavity (26 cm) configuration. Conversely, the

external optical injection exhibited weak locking

signature with improved linewidths by a factor of

1.6–2.8 and reaching as small as 70 and 87 pm for the

blue laser, respectively, while almost doubling in the

peak powers. Later, on–off keying modulation

technique based data transmission rates of up to 3.5

and 4.5 Gb/s are demonstrated on free-running blue

and red laser diodes, respectively, employing an in-

house laser diode mount based system. Moreover,

owing to the bandwidth limitation of the optically

injected systems, successful transmission of up to 2

Gb/s is demonstrated with better performance

compared to the respective free-running cases, in

particular, the external-optically injected system

demonstrated more than double improvement in the

bit-error-rate.

Single and Multiple Longitudinal Wavelength

Generation in Green Diode Laser Electrical and Computer Engineering, McGill University,

5620 Montreal, Quebec Canada H3A 0G4

CEMSE, King Abdullah University of Science and

Technology, Thuwal, Makkah Saudi Arabia 23955-6900

Electrical Engineering, King Abdullah University of Science

and Technology, 127355 Thuwal, Mecca Saudi Arabia

23955-6900

Electrical Engineering Department, King Fahd University of

Petroleum and minerals, Dhahran, Eastern Province Saudi

Arabia 31261

IEEE Journal of Selected Topics in Quantum Electronics

https://doi.org/10.1109/JSTQE.2019.2916870

Single and multiple wavelength laser systems are

presented that employ self-injection locked

InGaN/GaN green laser diode in an external cavity

configuration with a partially reflective mirror. A

stable and simultaneous locking of up to 4

longitudinal Fabry-Perot modes of the system cavity

is demonstrated with appreciable signal-to-noise-

ratio (SNR) of ~13 dB and average mode linewidth of

~150 pm. The multi-wavelength spectrum exhibited a

flat-top emission with nearly equal power

distribution among the modes and an analogous

mode spacing of ~0.5 nm. This first demonstration of

multi-wavelength generation source is highly

attractive in multitude of cross-disciplinary field

applications besides asserting the prospects of

narrow wavelength spaced multiplexed visible light

communication. Moreover, an extended two-stage

self-injection locked near single wavelength visible

laser system is also presented. An ultra-narrow

linewidth of ~34 pm is realized at 525.05 nm locked

wavelength from this novel system, with ~20 dB side-

mode-suppression-ratio (SMSR); thus signifying a

paradigm shift towards semiconductor lasers for near

single lasing wavelength generation, which is

presently dominated by other kinds of laser

technologies.

https://doi.org/10.1016/j.optcom.2019.05.034

https://doi.org/10.1109/JSTQE.2019.2916870


Tunable GaN photonic crystal and microdisk on

PDMS flexible film Department of Electrical and Electronic Engineering, The

University of Hong Kong, Pokfulam Road, Hong Kong

ACS Appl. Electron. Mater.

https://doi.org/10.1021/acsaelm.9b00114

Flexible micro-/nano-scale photonics has shown great

promise in a wide range of applications, especially

those that cannot be addressed by traditional

photonics based on rigid materials and structures.

Flexible photonics are typically implemented by

transferring compact optical devices made in high-

quality crystalline semiconductors onto plastic

substrates. However, success in developing flexible

optical devices based on GaN micro-/nano-structures

has been extremely limited. In this work, we target to

overcome this bottleneck by forming GaN photonic

crystals and microdisks on flexible PDMS films using a

combination of nano-/micro-sphere lithography and

laser lift-off techniques. The GaN-PDMS

configurations not only endow the devices with

mechanical flexibility but also enable optical tuning of

the photonic bandgaps from stretchable photonic

crystals and whispering-gallery-mode laser emission

from bendable microdisks over a remarkably large

range. Their optical properties of the devices are

extensively studied through a range of spectroscopy

techniques and simulations. The present

demonstrations verify the feasibility of the proposed

GaN-PDMS platform for forming compact flexible

devices, which could pave the way towards emerging

applications of flexible photonics technology.

Light confinement and high current density in UVB

laser diode structure using Al composition-graded p-

AlGaN cladding layer Asahi-Kasei Corporation, Fuji, Shizuoka 416-8501, Japan

Faculty of Science and Technology, Meijo University,

Nagoya 468-8502, Japan

Akasaki Research Center, Nagoya University, Nagoya 464-

8603, Japan

Applied Physics Letters

https://doi.org/10.1063/1.5095149

In this study, we investigated laser characteristics via

photoexcitation and electro-optical characteristics via

current injection in ultraviolet (UV)-B laser diodes. To

achieve light confinement and high current injection,

an Al composition-graded 260-nm thick p-type

Al0.9→0.45Ga0.1→0.55N cladding layer was

designed, which exhibited a calculated light

confinement factor of 3.5%. Laser oscillation with a

threshold at 275 kW/cm2 at 297 nm was obtained via

the photoexcited measurement. A prototype device

for current injection was designed using the p-

Al0.9→0.45Ga0.1→0.55N cladding layer and an

additional Al composition-graded 75-nm thick p-type

Al0.45→0Ga0.55→1N layer for the p-type contact

layer. The maximum current density in the device

reached 41.2 kA/cm2, which is the highest ever

reported value among light-emitting devices

operating in the UVB and ultraviolet-C regions. The

peak wavelength of the emission spectrum obtained

from the mirror facet was 300 nm, corresponding to

the double quantum wells, without any significant

droop. Further, a subpeak emission at 275 nm was

observed, which is likely caused by the waveguide

layer by electron overflow.

GaN-based ultraviolet microdisk laser diode grown

on Si Key Laboratory of Nano-Devices and Applications, Suzhou

Institute of Nano-Tech and Nano-Bionics, Chinese

Academy of Sciences, Suzhou 215123, China

University of Science and Technology Beijing, Beijing

100083, China

Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese

Academy of Sciences, Nanchang 330200, China

School of Nano Technology and Nano Bionics, University of

Science and Technology of China, Hefei 230026, China

Photonics Research

https://doi.org/10.1364/PRJ.7.000B32

This work reports a demonstration of electrically

injected GaN-based near-ultraviolet microdisk laser

diodes with a lasing wavelength of 386.3 nm at room

temperature. The crack-free laser structure was

epitaxially grown on Si substrates using an Al-

composed down-graded AlN/AlGaN multilayer buffer

to mitigate the mismatches in the lattice constant

and coefficient of thermal expansion, and processed

into “sandwich-like” microdisk structures with a

radius of 12 μm. Air-bridge electrodes were

successfully fabricated to enable the device electrical

https://doi.org/10.1021/acsaelm.9b00114

https://doi.org/10.1063/1.5095149



characterization. The electrically pumped lasing of

the as-fabricated microdisk laser diodes was

evidenced by the rapid narrowing down of

electroluminescence spectra and dramatic increase in

the light output power, as the current exceeded the

threshold of 248 mA.

Impact of quantum dots on III-nitride lasers: a

theoretical calculation of threshold current densities Institute for Nano Quantum Information Electronics, The

University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo,

153-8505, Japan


https://doi.org/10.7567/1347-4065/ab1068

We present a theoretical study on the gain and

threshold current density of III-nitride quantum dot

(QD) and quantum well (QW) lasers with a

comprehensive theory model. It is found that at

transparency condition the injection current density

of QD lasers is about 120 times lower than QW lasers

in III-nitrides, while in III-arsenide it is about 15 times.

It means that using QDs in III-nitride lasers could be 8

times more efficient than in III-arsenide. This

significant improvement in III-nitrides is due to their

large effective-masses and the large asymmetry of

effective-masses between valence bands and

conduction bands. Our results reveal the advantages

of using QD for low threshold laser applications in III-

nitrides.

Large-area, liftoff nanoporous GaN distributed Bragg

reflectors: Fabrication and application School of Microelectronics, Shandong University, Jinan

250100, China

School of Physics, Shandong University, Jinan 250100,

China

School of Science, Xi'an Polytechnic University, Xi'an

710048, China

Applied Surface Science

https://doi.org/10.1016/j.apsusc.2019.05.128

A facile one-step electrochemical etching based on

NaNO3 solution was developed for use in the

chemical lift-off nanoporous- (NP-) GaN distributed

Bragg reflectors (DBRs) over a macroscopic area

(>1 cm2). The reflectivity of the lift-off DBR mirror is

~85%, which is far lower than that (~97%) of the NP-

GaN DBR on the sapphire substrate. The decrease

should be attributed to light scattering due to higher

roughness in the lift-off mirror. To study its possible

applications, tris(8-hydroxyquinoline) aluminum (III)

(Alq3) thin film was grown on transferred NP-GaN

DBR mirror onto silicon substrate via a thermal

evaporation deposition. Compared to the reference

Alq3 thin film, the photoluminescence of the Alq3

thin film on the transferred mirror presents

significant enhancement and slight blue-shift, which

should be attributable to reflectivity enhancement by

the DBR and inner channel surface in the DBR mirror,

respectively.

Omnidirectional whispering-gallery-mode lasing in

GaN microdisk obtained by selective area growth on

sapphire substrate School of Physical Science and Technology, ShanghaiTech

University, Pudong, Shanghai, 201210, China

Ningbo Institute of Materials Technology and Engineering,

Chinese Academy of Sciences, Ningbo, 315201, Zhejiang,

China

University of Chinese Academy of Sciences, Beijing,

100049, China

School of Materials Science and Engineering, Shanghai

University, Shanghai, 200444, China

Department of Electrical and Electronic Engineering,

Faculty of Science and Engineering, University of

Nottingham Ningbo China, Ningbo 315100, China

Advanced Micro-Fabrication Equipment Inc. Shanghai,

201201, China

Optics Express

https://doi.org/10.1364/OE.27.016195

The optical properties of hexagonal GaN microdisk

arrays grown on sapphire substrates by selective area

growth (SAG) technique were investigated both

experimentally and theoretically. Whispering-gallery-

mode (WGM) lasing is observed from various

directions of the GaN pyramids collected at room

temperature, with the dominant lasing mode being

Transverse-Electric (TE) polarized. A relaxation of

compressive strain in the lateral overgrown region of

the GaN microdisk is illustrated by

photoluminescence (PL) mapping and Raman

spectroscopy. A strong correlation between the

crystalline quality and lasing behavior of the GaN

microdisks was also demonstrated.

https://doi.org/10.7567/1347-4065/ab1068


https://doi.org/10.1364/OE.27.016195


GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)

Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)

Characterization and optimization of MIS-HEMTs

device of high~k dielectric material on quaternary

barrier of Al0.42ln0.03Ga0.55N/UID-AIN/GaN/GaN

heterostructure for high power switching

application Department of Physics and Nanotechnology, Faculty of

Engineering and Technology, SRM Institute of Science and

Technology, Kattankulathur 603203, Chennai, India



In this study, the structure of efficient recessed gate

Metal Insulator Semiconductor High Electron Mobility

Transistor with Quaternary Barrier materials of

Al0.42ln0.03Ga0.55N was simulated and presented.

The device with heterostructure of

Al0.42ln0.03Ga0.55N/UID-AIN/GaN/GaN and

thickness of 5 nm/10 nm/40 nm/10 μm on SiC

substrate shows normally-OFF characteristics. The

effect of high~k dielectrics of HfAlxOx and the

quaternary barrier on the electrical performance of

the device was analyzed and compared with the

conventional AlGaN/GaN heterostructure. We found

that the charge optimization concept of the

polarization induced charges of the device 2DEG in

the channel was due to the combination of the

Quaternary Barrier of Al0.42ln0.03Ga0.55N and the

high~k dielectrics of HfAlxOx. Furthermore, the two

field plates used which are having a length of plate at

the drain (LGFP) of 1.8 μm and field plate at the

source (LGPS) 0.5 μm effectively spread the electric

field lines with the drain and showed a significant

improvement in the electrical properties of the

device and achieved a maximum drain current of

710 mA/mmV, low transconductance (gm) of 0.158

Smm−1 and high breakdown voltage of 570 V. In

comparison to the conventional AlGaN/GaN MIS-

HEMTs of similar design, the result of this Quaternary

Barrier Metal Insulator Semiconductor High Electron

Mobility Transistor (QB-MIS-HEMTs) exhibited a

better interface property, remarkable suppression of

leakage current, and excellent breakdown voltage

which are important for power switching

applications.

High-voltage vertical GaN-on-GaN Schottky barrier

diode using fluorine ion implantation treatment Suzhou Institute of Nano-tech and Nano-bionics, Chinese

Academy of Sciences, Suzhou 215123, PR China

School of Physical Science and Technology, ShanghaiTech

University, Shanghai 201210, PR China

University of Chinese Academy of Sciences, Beijing 100049,

PR China

Shanghai Institute of Ceramics, Chinese Academy of

Sciences, Shanghai 200050, PR China

Suzhou Nanowin Science and Technology Co., Ltd., Suzhou

215123, PR China

School of Nano Technology and Nano Bionics, University of

Science and Technology of China, Hefei 230026, PR China

AIP Advances

https://doi.org/10.1063/1.5100251

This paper reports on a high-voltage vertical GaN

Schottky barrier diode (SBD) using fluorine (F) ion

implantation treatment. Compared with the GaN SBD

without F implantation, this SBD effectively enhanced

the breakdown voltage from 155V to 775V and

significantly reduced the reverse leakage current by

105 times. These results indicate that the F-

implanted SBD showed improved reverse capability.

In addition, a high Ion/Ioff ratio of 108 and high

Schottky barrier height of 0.92 eV were also achieved

for this diode with F implantation. The influence of F

ion implantation in this SBD was also discussed in

detail. It was found that F ion implantation to GaN

could not only create a high-resistant region as

effective edge termination but be employed for

adjusting the carrier density of the surface of GaN,

which were both helpful to achieve high breakdown

voltage and suppress reverse leakage current. This

work shows the potential for fabricating high-voltage

and low-leakage SBDs using F ion implantation

treatment.


https://doi.org/10.1063/1.5100251


Characterization and modeling of 2DEG mobility in

AlGaN/AlN/GaN MIS-HEMT Univ. Grenoble Alpes, CEA-LETI, MINATEC, Grenoble,

France

Univ. Grenoble Alpes, IMEP-LAHC, MINATEC/INPG,

Grenoble, France

Microelectronic Engineering

https://doi.org/10.1016/j.mee.2019.05.003

We present a detailed study of the process influence

on two-dimensional electron gas (2DEG) transport

properties in Al0.25Ga0.75N/AlN/GaN

heterostructure. Hall effect measurements are used

to analyze the conduction in normally on devices

demonstrating the formation of a second channel at

the Al2O3/AlGaN interface for high biases. Electrical

characterization is performed on a large set of

devices for temperatures ranging from 25 °C to

250 °C, and 2DEG mobility is extracted using split C-V

measurement technique. Various technological splits

were experimentally tested and the corresponding

mobility characteristics were modeled using the

Kubo-Greenwood formula in order to determine the

dominant scattering phenomenon limiting the 2DEG

mobility.

A Rigorous Investigation of Electrostatic and

Transport Phenomena of GaN Double-Channel

HEMT Department of Electrical and Electronic Engineering,

Bangladesh University of Engineering and Technology,

Dhaka 1205, Bangladesh.


https://doi.org/10.1109/TED.2019.2915837

This paper presents a comprehensive investigation of

electrostatics and transport characterization of GaN

double-channel (DC) MOS-HEMT. Upon derivation of

a polynomial analytical expression establishing a

relationship between the Fermi level and the 2-D

electron gas density (2DEG), a relationship between

the sheet carrier density and applied gate voltage has

been obtained. To confirm the validity of the model

in both subthreshold and strong inversion regions,

the charge density profile and capacitance-voltage

profile have been attained from self-consistent

simulation incorporating the quantum mechanical

effect. The impact of GaN channel thickness on the

conduction band profile as well as charge density

profile has also been investigated. A 2-D analytical

model for current-voltage characteristics of GaN-DC-

MOS-HEMT has been developed for the first time.

Assuming velocity saturation of electrons in 2DEG,

the effects of spontaneous and piezoelectric

polarization at the heterointerface, field dependent

mobility, and the parasitic source and drain

resistance have been taken into account in evolution

of this model. The on-resistance extracted from the

analytical model was found to be 7.1 Ω·mm, which is

in close proximity with experimental results. A steep

subthreshold swing of 79 mV/dec was determined

from the current-voltage characteristics with an on-

off drain current ratio of the order of 10⁹, which

holds the promising application for enhancement

mode operation with minimal leakage current. For

corroboration, the derived results were compared

with experimental data acquired from the literature,

thereby enhancing the reliability of this model.

Effect of thermal cleaning prior to p-GaN gate

regrowth for normally-off high electron mobility

transistors School of Nano Technology and Nano Bionics, University of


Key Laboratory of Nanodevices and Applications, Suzhou

Institute of NanoTech and NanoBionics, Chinese Academy

of Science, Suzhou 215123, China

ACS Appl. Mater. Interfaces


This work studied the effect of thermal cleaning in

metal-organic chemical vapor deposition (MOCVD)

prior to p-GaN gate regrowth for normally-off high-

electron-mobility transistors (HEMTs). X-ray

photoelectron spectroscopy, capacitance-voltage

measurement and atomic force microscopy were

employed to identify the effects of thermal cleaning

before p-GaN regrowth. It was found that the

residual damages were hardly repaired at a relatively

low thermal cleaning temperature, while GaN

decomposition would occur at an excessively high

temperature. Thermal cleaning at 850 oC for 2 min in

MOCVD can effectively remove the surface

contamination and alleviate the etch damage without

causing any significant deterioration of the AlGaN

https://doi.org/10.1016/j.mee.2019.05.003

https://doi.org/10.1109/TED.2019.2915837



barrier. And the Dit in p-GaN gate was reduced from

1012~1013 to 1011~1012 eV-1·cm-2, resulting in a

low gate reverse leakage of 0.1 nA/mm @ VDS-

OFF=180 V, a high Ion/Ioff ratio of 4×1010, and a

relatively high threshold voltage of +1.7 V @ ID=10

μA/mm.

Formation of conductive AlN buffer layer using

spontaneous via-holes and realization of vertical

AlGaN Schottky diode on a Si substrate Research Organization of Science and Technology,

Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga

525-8577, Japan


https://doi.org/10.1063/1.5058110

A conductive AlN epitaxial layer is successfully

realized by spontaneously forming via-holes filled

with n-AlGaN inside an AlN buffer layer on a Si

substrate. The via-holes are found to originate from

the formation of an Al–Si alloy, produced from a

small amount of Al supplied to the Si substrate at the

initial stage of the crystal growth of the n-AlN buffer

layer using metal organic chemical vapor deposition

and successive selective growth of n-AlN on the Si

surface. The via-holes are filled with conductive n-

AlGaN by successive epitaxial growth of n-AlGaN,

making the insulating n-AlN buffer layer conductive.

The vertical conductivity through this n-AlN buffer

layer is enhanced more than 540 times compared

with an n-AlN buffer layer without via-holes. Using

this conductive n-AlN buffer layer on the Si substrate,

we successfully fabricated a vertical n-AlGaN Schottky

diode on the Si substrate for the first time.

A large-signal Pspice modeling of GaN-based MIS-

HEMTs School of Advanced Materials and Nanotechnology, Xidian

University, Xi'an 710126, China

Key Laboratory of Microelectronics Devices and Integrated

Technology, Institute of Microelectronics of Chinese

Academy of Sciences, Beijing 100029, China

Superlattices and Microstructures

https://doi.org/10.1016/j.spmi.2019.05.023

In this work we present a physics-based semi-

empirical large-signal model for GaN MIS-HEMTs,

which introduces the non-segmented, smooth

continuous equations to describe the static and

dynamic characteristics of GaN MIS-HEMTs in

different working regions. The unique physical effect

of threshold voltage drift was considered for MIS-

HEMTs in the current model, in addition to effects of

the channel length modulation and the temperature

drift. In addition, a current-controlled current source

was used in the dynamic model to characterize the

nonlinear capacitance including the gate-drain

capacitance CGD, gate-source capacitance CGS and

drain-source capacitance CDS at different operating

voltages. The model is in excellent agreement with

the experimental data for both drain current and

capacitances over a typical range of applied voltages

and temperatures.

Comparative Study Between Partially and Fully

Recessed‐Gate Enhancement‐Mode AlGaN/GaN MIS

HEMT on the Breakdown Mechanism State Key Discipline Laboratory of Wide Band-gap

Semiconductor Technology, School of Microelectronics,

Xidian University, Shaanxi 710071, People’s Republic of

China

School of Physics and Optoelectronic Engineering, Xidian

University, Shaanxi 710071, People’s Republic of China



In this paper, two enhancement‐mode (E‐mode)

AlGaN/GaN recessed‐gate MIS devices with the in

situ N2 plasma treatment, known as partially

recessed‐gate metal insulator semiconductor (MIS)

device and fully recessed‐gate MIS device, are

designed. Among them, the partially recessed‐gate

MIS device shows excellent characteristics that the

threshold voltage of +3.5 V, saturation current

density of 722 mA mm−1, peak transconductance of

212 mS mm−1, and the power figure of merit of

4.39 × 108 W cm−2 which is the highest value in

E‐mode AlGaN/GaN MIS device with the threshold

voltage greater than 3 V. Moreover, the current

collapse and breakdown voltage of partially

recessed‐gate MIS device and fully recessed‐gate MIS

device are investigated, and Silvaco simulation is

carried out to analyze the difference of breakdown

mechanism between two structure devices. Through

the analysis of five main breakdown leakage paths,

we can get the conclusion that the factor causing the

https://doi.org/10.1063/1.5058110




breakdown voltage difference between partially

recessed‐gate MIS device and fully recessed‐gate MIS

device is the difference in the width of depletion

region of the two devices.


GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)

Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)

Cl2/Ar based atomic layer etching of AlGaN layers III-V Lab, 1 Avenue Augustin Fresnel, 91767 Palaiseau,

France

Institut d’Electronique, de Microélectronique et de

Nanotechnologie, Avenue Henri Poincaré, 59652

Villeneuve d’Ascq, France

Journal of Vacuum Science & Technology A

https://doi.org/10.1116/1.5090106

This paper reports on atomic layer etching of several

III-N materials such as GaN, AlN, AlGaN, and InAlGaN

based on a sequential surface modification by

chlorine adsorption followed by a low energy Ar

plasma exposure to remove the modified layer using

a reactive ion etching system. A study on the

influence of several parameters, such as gas flow

rates, removal step duration, RIE power and number

of cycles on the etch per cycle, and the root-mean-

square roughness, is performed. Low etch per cycle

from 0.17 to 1.85 nm/cycle, respectively, for AlGaN

and GaN and surfaces as smooth as the as-grown

samples were obtained. The developed process is

intended to be used for normally off GaN-based high

electron mobility transistor processing.

Analysis of Gain Variation with Changing Supply

Voltages in GaN HEMTs for Envelope Tracking Power

Amplifiers Centre for High Frequency Engineering (CHFE), School of

Engineering, Cardiff University, Cardiff CF10 3AT, U.K.

Manufacturing Engineering Centre, Cardiff University,

Cardiff CF10 3AT, U.K.

Department of Electronic and Electrical Engineering,

University of Sheffield, Sheffield S10 2TN, U.K.

IEEE Transactions on Microwave Theory and Techniques

https://doi.org/10.1109/TMTT.2019.2916404

Envelope tracking (ET) is a promising power amplifier

(PA) architecture for current and future

communications systems, which uses dynamic

modulation of the supply voltage to provide high

efficiency and potentially very wide bandwidth over a

large dynamic range of output power. However, the

dynamic nature of the supply voltage can lead to a

problematic variation in transistor gain, particularly in

GaN HEMTs. This paper describes and analyzes this

behavior and the detrimental effect it can have on ET

PAs. Contributing factors and origins of gain variation

are described in detail along with how, for the first

time, meaningful comparisons can be made between

different devices. Using these guidelines, gain

variation is shown to be a widespread issue effecting

most GaN HEMTs presented in literature. To allow an

analysis of the intrinsic device behavior, an extended

transistor model is developed that takes the effect of

gate and source field plates into account. This model

is refined using measurement data and used to

demonstrate the fact that the parasitic gate-drain

capacitance (CGD) is the main contributor to the

small-signal gain variation--a significant part of the

overall gain variation. Based on this knowledge,

possible strategies to reduce gain variation at the

transistor technology level are proposed, allowing the

optimization of GaN HEMTs specifically for ET PAs.

One identified strategy involves reducing the length

of the gate field plate and is shown to be a viable

approach to reduce the gain variation in GaN HEMTs,

albeit at an increased RF/dc dispersion.

A Fully Integrated C-band GaN MMIC Doherty Power

Amplifier with High Efficiency and Compact Size for

5G Application Department of Electronic Engineering, Tsinghua University,

Beijing, 100084, China

Intelligent RF Radio Laboratory (iRadio Lab), University of

Calgary, AB T2N 1N4, Canada

IEEE Access

https://doi.org/10.1109/ACCESS.2019.2919603

This paper presents a fully integrated C-band Doherty

power amplifier (DPA) based on a 0.25-μm GaN-

HEMT process for 5G massive MIMO application. The

performance degradation caused by nonlinear output

capacitance is analyzed, and a novel compensation

technique is proposed. A low-Q output network is

employed to broaden the bandwidth, and its

https://doi.org/10.1116/1.5090106




insertion loss in the back-off region is demonstrated

to be mainly decided by the Q-factor of the drain bias

inductor of the main PA. Hence, by adopting on-chip

transmission lines with high Q-factors for drain

biasing, a full integration and a low loss can be

achieved simultaneously. Reversed uneven power

splitting and back-off input matching are proposed

for gain enhancement. The fabricated DPA

demonstrates a small-signal gain of 8.6 -11.6 dB, an

output power of 40.4 -41.2 dBm, a 6-dB back-off

drain efficiency (DE) of 47% -50%, and a saturation DE

of 55% -63% across a wide bandwidth from 4.5 to 5.2

GHz, with an ultra-compact size of 2.2 mm × 2.1 mm.

Using a 40-MHz LTE signal with a 7.7-dB peak-to-

average power ratio at the carrier frequency of 4.9

GHz, the measured average output power and

efficiency are 33 dBm and 43%, respectively. The raw

adjacent channel power ratio is -29 dBc, and is

improved to -46 dBc by applying digital predistortion.

930 kA/cm2 peak tunneling current density in

GaN/AlN resonant tunneling diodes grown on

MOCVD GaN-on-sapphire template U.S. Naval Research Laboratory, Washington, DC 20375,

USA

Department of Electrical and Computer Engineering, The

Ohio State University, Columbus, Ohio 43210, USA

Departments of Physics and Electrical Engineering, Wright

State University, Dayton, Ohio 45435, USA

Lincoln Laboratory, Massachusetts Institute of Technology,

Lexington, Massachusetts 02421, USA

Applied Physics Letters

https://doi.org/10.1063/1.5095056

We report on the design and fabrication of ultrahigh

current density GaN/AlN double barrier resonant

tunneling diodes grown via rf-plasma assisted

molecular-beam epitaxy. The device structure was

grown on a metal-organic chemical vapor deposition

GaN-on-sapphire template. The devices displayed

repeatable room temperature negative differential

resistance with peak tunneling current densities (Jp)

between 637 and 930 kA/cm2. Analysis of

temperature dependent measurements revealed the

presence of severe self-heating effects, which allow

strong phonon scattering that deteriorates the

electron quantum transport. Finally, a qualitative

comparison to the same structure grown on a low

dislocation density freestanding GaN substrate has

shown that sapphire-based templates are a feasible

alternative.

Temperature‐dependent small signal performance

of GaN‐on‐diamond HEMTs School of Electronic Science and Engineering, University of

Electronic, Science and Technology of China, Chengdu,

China

Key Laboratory of Integrated Circuits, Nanjing Electronic

Devices Institute, Nanjing, China

International Journal of Numerical Modelling: Electronic

Networks, Devices and Fields

https://doi.org/10.1002/jnm.2620

This paper presents the temperature dependence of

small signal performance of GaN‐on‐diamond high

electron mobility transistors (HEMTs) at an ambient

temperature range from 0°C to 125°C. The

temperature influence on the parasitic resistances

together with the intrinsic parameters is investigated,

and the temperature coefficients of these parameters

are extracted from measured data. For comparison, a

GaN‐on‐SiC device is also investigated. These results

are important for the development and application of

the GaN‐on‐diamond HEMT technology.

1/f noise characteristics of AlGaN/GaN HEMTs with

periodically carbon-doped GaN buffer layer Advanced Material Research Center, Kumoh National

Institute of Technology, Gumi 39177, Republic of Korea

Department of Advanced Materials Science and

Engineering, Kumoh National Institute of Technology,

Gumi 39177, Republic of Korea

School of Electronics Engineering, Kyungpook National

University, Daegu 41566, Republic of Korea


https://doi.org/10.1016/j.mee.2019.110985

We investigate the DC and 1/f noise properties in

Al0.25Ga0.75N/GaN high-electron mobility

transistors (HEMTs) with two types of 2 μm-thick

periodically carbon-doped GaN buffer layer (PC-

doped GaN buffer) with and without inserting the

30 nm-thick Al0.05Ga0.95N back barrier layer

between the GaN channel layer and the PC-doped

GaN buffer. The PC-doped GaN buffer layer consists

of multiple layers of 12 nm-thick C-doped GaN layer

https://doi.org/10.1063/1.5095056




with doping concentration of 1 × 1018 cm−3 and

50 nm-thick undoped GaN layer with unintentional n-

typing concentration of 2 × 1016 cm−3. A reference

AlGaN/GaN HEMT with 2 μm-thick highly-resistive

GaN buffer layer without C-doping is also fabricated

for comparison. Similarly to the reference AlGaN/GaN

HEMT, the AlGaN/GaN HEMTs with PC-doped GaN

buffer show typical 1/f noise characteristics mainly

due to the trapping effects at the AlGaN/GaN

interface from subthreshold region to strong-

accumulation region, which indicates that the deep

trapping effects in the PC-doped GaN buffer layer is

negligible, and experience the correlated mobility

fluctuations (CMF), which is convinced from the drain

current power spectral density (PSD) versus drain

current. At off-state (deep-subthreshold region), on

the other hand, the HEMTs with the PC-doped GaN

buffer layer exhibit 1/f2 noise characteristics, which

are closely related to the generation-recombination

(g-r) noise caused by the spatial trapping/detrapping

process between the deep acceptor in the C-doped

layer and the shallow donor in the undoped layer in

the PC-doped GaN buffer, while the reference HEMT

still shows typical 1/f noise characteristics.

The influence of dielectric layer on the thermal

boundary resistance of GaN‐on‐diamond substrate Institute for Advanced Materials and Technology,

University of Science andTechnology Beijing, Beijing, China

Science and Technology on Monolithic Integrated Circuits

and Modules Laboratory, Nanjing Electronic Devices

Institute, Nanjing, China

Institute of Engineering Thermophysics, Chinese Academy

of Sciences, Beijing, China

College of Pipeline and Civil Engineering, China University

of Petroleum (East China), Qingdao, China

Surface and Interface Analysis

https://doi.org/10.1002/sia.6649

The cooling behavior of GaN‐on‐diamond substrate

can be enhanced by reducing the thermal boundary

resistance (TBR), which is mainly determined by the

nature of interlayer. Although SiN film is considered

as the primary candidate of dielectric layer, it is still

needed to be optimized. In order to facilitate the

understanding of the influence of dielectric layer on

the TBR of GaN‐on‐Diamond substrate, aluminum

nitride (AlN), and silicon nitride (SiN) film were

compared systematically, both of which are 100 nm.

The time‐domain thermoreflectance (TDTR)

measurements, adhesion evaluation, and

microstructural analysis methods were adopted to

analyse these two interlayers. The results show the

TBR of SiN interlayer is as low as 38.5 ± 2.4 m2K

GW−1, comparing with the value of 56.4 ± 5.5 m2K

GW−1 for AlN interlayer. The difference of TBR

between these two interlayers is elucidated by the

diamond nucleation density, and the adhesion

between the diamond film and GaN substrate, both

of which are affected by the surface charge and

chemical groups of the dielectric layer.

A systematic study of device structure on DC and

small‐signal characteristics of millimeter‐wave

AlGaN/GaN HEMT State Key Discipline Laboratory of WideBand‐gap

Semiconductor Technology, School of Microelectronics,

Xidian University, Xi'an, China

School of advanced materials and technology, Xidian

University, Xi'an, China

International Journal of Numerical Modelling: Electronic

Networks, Devices and Fields


In this paper, the relationship between the gate

structure, passivation structure, short‐channel effect,

source‐drain distance, DC, and the small‐signal

characteristic of a device is studied through

simulations. By studying the gate structure and

passivation layer, it is concluded that the operating

frequency of a device increases as the gate length

decreases. However, as the gate length decreases,

the gate resistance becomes the main factor

restricting the small‐signal performance. In order to

solve the contradiction between the gate resistance

and gate length, a T‐shaped gate structure is studied,

in which the gate height, gate cap, and passivation

layer thickness are optimized. It is found that when

the gate height and gate cap are 120 and 500 nm,

respectively, the parasitic capacitance introduced by

the gate cap can be minimized. Meanwhile, the

influence of gate resistance on the small‐signal gain

can also be reduced. Besides, the short‐channel

effect is analyzed, and the scheme for improving the

short‐channel effect is proposed. By analyzing the

source‐drain distance, and considering the influence

https://doi.org/10.1002/sia.6649



of parasitic capacitance and resistance on the

small‐signal characteristic, the gate‐source spacing is

determined to be 0.9 μm. The design of a gate‐drain

spacing is mainly based on the influence of a

breakdown voltage; therefore, the gate‐drain spacing

should be 1.5 to 2 μm.

Assessing the Role of Fluorine in the Performance of

AlxGa1−xN/GaN High-Electron-Mobility Transistors

from First-Principles Calculations Microsystem and Terahertz Research Center, China

Academy of Engineering Physics, Chengdu 610200, China

Institute of Electronic Engineering, China Academy of

Engineering Physics, Mianyang 621999, China

Department of physics, School of Science, Wuhan

University of Technology, Wuhan 430070, China

Physical Review Applied

https://doi.org/10.1103/PhysRevApplied.11.054021

Doping fluorine (F) into the AlxGa1−xN layer is critical

to the performance of enhancement-mode

AlxGa1−xN/GaN high-electron-mobility transistors

(HEMTs). However, the understanding of the role of F

in, AlxGa1−xN/GaN HEMTs is rather limited. Using the

first-principles-calculated defect formation energies

and transition energy levels, combined with the

special quasirandom structure approach and the

detailed balance theory, we investigate the

interaction between F and native defects and

impurities, as well as its effect on the Fermi energy of

the AlxGa1−xN alloy. Our results suggest that F is

incorporated as F−i in the AlxGa1−xN layer, which

exhibits auto n-type conductivity because of

unintentionally induced oxygen (O). F doping causes

the redistribution of the charge states of intrinsic

defects and impurities, and thus the Fermi energy of

the AlxGa1−xN layer. The charge-redistribution

depends on the difference between the

concentrations of F and O. Finally, we reveal the

mechanism for the change of the electronical

performance of

AlxGa1−xN/GaN HEMTs after F doping. The positive

shift of the threshold voltage is related to the

negatively charged F i. Only when the concentration

of F is higher than that of unintentionally induced O

in AlxGa1−xN, F begins to increase the surface

potential and the Schottky barrier height of

AlxGa1−xN/GaN HEMTs.

Study of high Al fraction in AlGaN barrier HEMT and

GaN and InGaN channel HEMT with In0.17Al0.83N

barrier Department of Electronics and Communication

Engineering, Birla Institute of Technology, Mesra, India

Microsystem Technologies

https://doi.org/10.1007/s00542-019-04466-4

This paper investigates to find a method to improve

the design parameters such as drain current,

transconductance, cut off frequency and most

importantly minimum noise figure of the Nitride

HEMTs. Firstly, to improve the performance of the

Nitride HEMT, the AlGaN barrier with high Al fraction

was used. Owing to its higher carrier density at higher

Al fraction, AlGaN/GaN HEMT exhibited higher drain

current, higher transconductance. It also results in a

lower minimum noise figure. But, the increase of Al in

barrier leads to a lattice mismatch of barrier layer

with GaN channel layer. Thus, In0.17Al0.83N barrier

layer which is lattice matched to GaN is used instead

of traditionally popular AlGaN. Along with a change

of material of the barrier layer, a change of material

of the channel layer shows improvement in DC & RF

response and most importantly in the minimum noise

figure when InGaN replaces GaN. The noise

performance has been further improved with the T-

shaped gate by reducing the gate resistance. All the

theoretical analyses have been supported and

verified by the results obtained from simulation

carried out using Silvaco TCAD tool.

Supply- and Load-Modulated Balanced Amplifier for

Efficient Broadband 5G Base Stations Department of Electrical, Computer and Energy

Engineering, University of Colorado Boulder, Boulder, CO

80304 USA.

Department of Electrical, Electronic, and Information

Engineering, University of Bologna, 40136 Bologna, Italy.

School of Engineering, Cardiff University, Cardiff CF10 3AT,

U.K.



This paper presents a broadband efficient power

amplifier (PA) targeting sub-6-GHz 5G base station

applications. Due to the demanding requirements in

both peak-to-average power ratio (PAPR) and

https://doi.org/10.1103/PhysRevApplied.11.054021

https://doi.org/10.1007/s00542-019-04466-4



bandwidth in 5G systems, we employ a combination

of both load and supply modulation for efficiency

enhancement. Active matching, implemented using

an RF-input load-modulated balanced amplifier

(LMBA) architecture, enables efficient octave-

bandwidth operation. Supply modulation, which is

carrier frequency agnostic, is then used to further

extend the back-off efficiency. This paper focuses on

a study of supply modulation strategies for the load-

modulated PA using an efficient GaN eight-level

discrete supply modulator. To overcome the

bandwidth limitations associated with discrete-level

switching, a commutation rate reduction (CRR) filter

is applied in digital baseband and its effects are

analyzed theoretically and experimentally. The

supply-modulated LMBA is characterized across 1.8-

3.8 GHz with 100-MHz, 10-dB PAPR signals. An output

power of 34 dBm with average composite (total) PAE

ranging from 22.4% to 43.9% across the band is

demonstrated, with an ACLR of about -50 dBc after

digital predistortion.

Analytical Design Space of Power Amplifiers

Including the Class-A/B/J Continuum for Dynamic

Load Modulation IRadio laboratory, University of Calgary, Calgary, AB,

T2N1N4 Canada

School of Information and Communication Engineering,

University of Electronic Science and Technology of China,

Chengdu, 611731 China

IEEE Access


In this work, an analytical design space of power

amplifiers (PAs) including the Class-A/B/J continuum

for dynamic load modulation (DLM) at the current

generator plane (CGP) is proposed based on the

theory of load modulated (LM) continuous Class-B/J

PAs. By introducing a biasing operation factor q, the

theory of DLM PAs provides an analytical design

space for all the operation modes from Class-B/J

mode to Class-A mode. The analytical design space of

DLM PAs shows that high efficiency is maintained at a

large dynamic range of output power back-off (OPBO)

with a purely resistive load modulation at the CGP

when Class-B/J mode is performed. For deep Class-AB

mode, the analytical design space of DLM PAs shows

that a combination of resistive and reactive load

modulation at the CGP is used to maintain the high

efficiency at OPBO. The effectiveness of proposed

analytical design space is validated by load-pull

measurements of a bare-chip gallium nitride (GaN)

device.

Optimized Load Trajectory for Finite Peaking scOFF-

State Impedance-Based Doherty Power Amplifiers School of Electrical, Computer, and Energy Engineering,

Arizona State University, Tempe, AZ 85287 USA

IEEE Microwave and Wireless Components Letters

https://doi.org/10.1109/LMWC.2019.2915998

This letter presents an optimized load trajectory for

symmetrical Doherty power amplifiers (DPA) with

finite peaking off-state output impedance. This

presented architecture uses the transistor's nonlinear

phase distortion (NPD) to enhance the average drain

efficiency (DE) of the DPA with the proper choice of

carrier and peaking power amplifier (PA) load

trajectories. A gallium nitride (GaN)-based DPA

operating at 2.2 GHz has been designed and

fabricated using the presented design methodology.

The DPA delivers 43 dBm of output power at 3-dB

compression (P-3 dB) and exhibits a DE of 55.5% at 9-

dB OBO under continuous wave (CW) excitation. The

DPA achieves average DE of 55% with linearized

adjacent channel power ratio (ACPR) of -56.0 dBc

with a 20-MHz LTE signal. This letter demonstrates

that NPD in a DPA with finite peaking off-state

impedance can be used to achieve excellent back-off

efficiency and linearity.

A Study on Quadratic PHD Models for Large Signal

Applications Institute of Electrodynamics, Microwave and Circuit

Engineering, TU Wien, 1040 Vienna, Austria



Measurement-based black box behavioral models are

widely used nowadays. To handle nonlinear effects

efficiently, such models often rely on approximation

techniques. Polyharmonic distortion (PHD) modeling

emerged as a viable approach for describing a

nonlinear mapping. Typical PHD-based models, such

as the well-known X-parameter model, are gained


https://doi.org/10.1109/LMWC.2019.2915998



from linearization while operating on a certain large

signal (LS) operational point. This limits the accuracy,

especially for hard nonlinearities. However, quadratic

terms can be added, which result in the quadratic

PHD (QPHD) model. This enables highly accurate

models for devices in strongly nonlinear operation,

even in highly mismatched environments. In this

paper, the accuracy of such models is investigated by

predicting typical nonlinear measures, such as load-

pull contours and intermodulation distortion, to

assess the model accuracy for both static and

dynamic stimulus. Furthermore, the LS matching

problem is solved for both the X-parameter and the

QPHD model. This allows to predict the optimum

matching analytically, without performing load-pull

analysis. To verify the accuracy of the model, the

results are presented by comparing the model

prediction with verification measurements for a

commercially available GaN HEMT.

A p-Channel GaN Heterostructure Tunnel FET With

High ON/OFF Current Ratio Department of Electronic and Electrical Engineering, The

University of Sheffield, Sheffield S3 7HQ, U.K..


https://doi.org/10.1109/TED.2019.2915768

A novel mechanism to achieve a nonambipolar tunnel FET (TFET) is proposed in this paper. The method relies on polarization charge induced in semiconductors, such as group III nitrides, to enhance the electric field across the junction and facilitate unidirectional tunneling based on the polarity of the applied gate bias. This also enables enhanced control over the tunneling distance, reducing it significantly in comparison to a conventional TFET. The proposed p-channel device implemented in a novel vertical GaN nanowire geometry facilitates a reduction of footprint while still maintaining comparable performance to that of conventional E-mode p-channel devices in GaN. This opens up possibilities for E-mode p-channel GaN devices.

https://doi.org/10.1109/TED.2019.2915768


GROUP 5 – MEMS and Sensors Group leader: Marc Faucher (IEMN) Information selected by Knowmade

Electrical Modulation of Narrowband GaN/AlGaN

Quantum-Well Photonic Crystal Thermal Emitters in

Mid-Wavelength Infrared Department of Electronic Science and Engineering and

Photonics and Electronics Science and Engineering Center,

Kyoto University, Kyoto 615-8510, Japan

ACS Photonics

https://doi.org/10.1021/acsphotonics.9b00440

Narrowband thermal emitters operating in the mid-

wavelength infrared (MWIR, 3–8 μm) are important

for spectroscopic sensing systems in various fields of

research such as chemistry, healthcare, and

environmental science. To increase the signal-to-

noise ratio in these spectroscopic applications, it is

required that only thermal emission in a narrow

target wavelength range be modulated electrically

while other wavelength components are

unmodulated. In addition, an increase of the

emitter’s temperature is highly desired for high-

power operation in the MWIR. To date, a number of

efforts have been put into the demonstration of

electrical modulation of thermal emission by using

semiconductors, phase-change materials, and

graphene. However, these emitters have not

achieved selected modulation of narrowband thermal

emission in the MWIR at high temperatures. Here, we

demonstrate the electrical modulation of a

narrowband MWIR thermal emission at high

temperatures of up to 500 °C using GaN/AlGaN

multiple quantum well (MQW) photonic crystals. Our

emitter exhibits a narrowband thermal emission (Q =

40) owing to the combination of intersubband

absorption in the MQWs and optical resonances of

the photonic crystals, the intensity of which can be

electrically modulated at high speed (50 kHz) through

the control of the electron density in the MQWs. Our

demonstration of electrical modulation of MWIR

narrowband thermal emitters at high temperature

will accelerate the practical use of narrowband

thermal emitters in various spectroscopy applications

such as optical gas sensors, including CO2 sensors.

Design and implementation of bound-to-quasibound

GaN/AlGaN photovoltaic quantum well infrared

photodetectors operating in the short wavelength

infrared range at room temperature Department of Electrical Engineering, Technion-Israel

Institute of Technology, Haifa 32000, Israel

Univ. Grenoble-Alpes, CEA, INAC, PHELIQS, 17 av. des

Martyrs, 38000 Grenoble, France

Univ. Grenoble-Alpes, CNRS-Institut Néel, 25 av. des



https://doi.org/10.1063/1.5079408

In this paper, we discuss the design of photovoltaic

quantum well infrared photodetectors (QWIPs) based

on polar GaN/AlGaN multiquantum wells (MQWs).

Getting a reasonable escape probability of the

excited electron requires adjusting the bound-to-

quasibound intersubband transition in the absorbing

quantum well and engineering the polarization-

related internal electric field in the barriers. This can

be achieved with a MQW period that consists of 3

layers, namely, the active quantum well, an

extraction barrier, and an injection barrier, the latter

being thin enough to allow tunneling transport.

Following this design scheme, we demonstrate

bound-to-quasibound GaN/AlGaN QWIPs with peak

photocurrent response at 2.3 μm, operating at room

temperature in both photovoltaic and

photoconductive modes. Based on high-resolution x-

ray diffraction measurements, the entire detector

structure, which included a 40-period MQW with

30 nm-thick barriers, along with top and bottom

contact layers of combined thickness above 900 nm,

was grown pseudomorphically on an AlGaN-on-

sapphire template. A room-temperature responsivity

of 88 μA/W was measured at zero bias, increasing up

to 302 μA/W at −1.0 V bias. The responsivity reached

its maximum at 150–200 K, where it was

approximately a factor of 2 higher than at room

temperature. Ideas for a new device structure to

improve the QWIP response in the photovoltaic

mode are proposed.

https://doi.org/10.1021/acsphotonics.9b00440

https://doi.org/10.1063/1.5079408


Design and analysis of plasmonic sensor in

communication band with gold grating on nitride

substrate Department of Applied Sciences (Physics Division),

National Institute of Technology Delhi, 110040, India



Grating coupled nanostructures are integral part of

advanced plasmonic sensors for bio-sensing

applications. In this work, gold gratings on dielectric

substrate (e.g., GaN, AlN, and Si3N4) based plasmonic

sensor is simulated and analyzed in optical

communication band for refractive index sensing with

spectral interrogation. The sensor simulation is

carried out with rigorous coupled wave analysis

(RCWA). The influence of grating variables on

resonance behavior and sensing performance of the

grating structure is also studied. A significantly large

sensitivity of 1140 nm/RIU is achieved with a very

high precision (in terms of as small curve width as

4.20 nm). The results indicate that Au grating on GaN

substrate can provide a high sensing performance for

a broad range of analyte refractive indices. The

sensor provides comparatively better performance

than the existing grating based plasmonic sensors.

The possibility of self-referenced sensing is also

explored.

Flexible and Transparent Aluminum‐Nitride‐Based

Surface‐Acoustic‐Wave Device on Polymeric

Polyethylene Naphthalate Center for Biomolecular Nanotechnologies, Istituto Italiano

di Tecnologia, Via Barsanti snc, Arnesano 73010, Italy

Department of Innovation Engineering, University of

Salento, Campus Ecotekne, Via Monteroni, Lecce 73100,

Italy

Materials Characterization Facility, Istituto Italiano di

Tecnologia, Via Morego 30, Genova 16163, Italy

Advanced Electronic Materials

https://doi.org/10.1002/aelm.201900095

The development of wearable technology

increasingly requires bendable sensing devices

operating across multiple domains for

opto‐electro‐mechanical and biochemical

transduction. Piezoelectric materials integrated into

flexible and transparent device architectures can

enable multiple‐sensing platforms. It is shown that

flexible and compliant surface‐acoustic‐wave (SAW)

piezoelectric devices include all these features and

can be applied to the human body. A flexible and

transparent aluminum‐nitride‐(AlN)‐based SAW

device on a thermoplastic polyethylene naphthalate

(PEN) substrate, fabricated by low‐temperature

sputtering deposition of a multilayered AlN‐based

stack, is reported for the first time. Two resonant

modes, corresponding to Rayleigh and Lamb wave

propagation, are shown and compared with a control

SAW device on a silicon substrate. A large

transmission‐signal amplitude, up to 20 dB, is

achieved for the Lamb resonance mode around 500

MHz at an acoustic velocity of 10 500 m s−1. The

technology is applied to the fabrication of a wearable

temperature sensor. Compared to the same

piezoelectric stack and SAW technology onto silicon

substrates, the AlN/PEN SAW shows better

performance and a temperature coefficient

frequency as high as ≈810 ppm °C−1. The potential of

this flexible SAW device as a wearable temperature

sensor based on Rayleigh modes is demonstrated.

Hydrogen sensing performance of a GaN-based

Schottky diode with an H2O2 treatment and

electroless plating approach Department of Chemical Engineering, National Cheng Kung

University, Tainan 70101, Taiwan, Republic of China

Institute of Microelectronics, Department of Electrical

Engineering, National Cheng Kung University, Tainan

70101, Taiwan, Republic of China

Department of Computer Science and Information

Engineering, Chaoyang University of Technology, Taichung

41349, Taiwan, Republic of China

Sensors and Actuators B: Chemical

https://doi.org/10.1016/j.snb.2019.05.076

A new electroless plating (EP)-Pd/GaOx/GaN Schottky

diode-type hydrogen sensor is fabricated and

comprehensively studied herein. The GaOx dielectric

is formed as a result of a proper H2O2 treatment on

the GaN surface. In addition, a 20-period

sensitization/activation process and an appropriate

EP approach of the Pd catalytic layer are employed to

facilitate a high-performance metal-semiconductor

(M-S) Schottky contact. Experimentally, an extremely


https://doi.org/10.1002/aelm.201900095

https://doi.org/10.1016/j.snb.2019.05.076


high hydrogen sensing response of 5.5 × 106 (under

1% H2/air gas) and a relatively low detection limit of

5 ppm H2/air are obtained at 300 K. The

corresponding response and recovery times are 22 s

and 21 s at 300 K, respectively. A new data

transmission algorithm based on the Kalman

algorithm is also proposed in this work. According to

the simulation results, the data transmission volume

can be reduced by 90%. The average recovery error

rate is less than 0.38%. Furthermore, our developed

reduced redundancy method can pre-warn the user

of sensor failure. Based on the advantages

mentioned above, therefore, the studied device is

promising for high-performance hydrogen sensing

and Internet of Things (IoT) applications.

Characterization of highly textured piezoelectric AlN

films obtained from aluminum and ammonium

chloride by a simple vapor deposition process Institute of Microelectronics Technology and High-Purity

Materials, Russian Academy of Science, Chernogolovka,

Moscow District, 6 Academician Ossipyan Str, 142432,

Russia

Thin Solid Films

https://doi.org/10.1016/j.tsf.2019.05.049

We report a simple and efficient deposition

technique for the growth of highly-textured AlN thin

films. The proposed chloride-based chemical vapor

deposition approach is based on widely available

precursors and an unsophisticated experimental set-

up. The films were characterized by electron

microscopy, X-ray diffraction, Raman spectroscopy

and cathodoluminescence. We studied the

correlations between the deposition conditions and

the properties of the resulting films, such as

morphology, microstructure, features of the Raman

spectra, and piezoelectric characteristics. In

particular, we show that the minimum of the Raman

bands A1(TO)/ E2(h) intensity ratio, under excitation

along c-axis, corresponds to the maximum of the

piezoelectric coefficient. The films deposited under

the optimized conditions are composed of well-

aligned column-like crystallites. These films have a

piezoelectric coefficient of 5.5–6.5 pC/N, which

approaches the highest values reported for this

material. The simplicity, efficiency and high quality of

the resulting films make the proposed deposition

approach highly interesting for a wide range of

practical applications.

Solution-processed Au@rGO/GaN nanorods hybrid-

structure for self-powered UV, visible photodetector

and CO gas sensors Department of Physics, Chungnam National University,

Daejeon, 34134, Republic of Korea

b

Sungkyunkwan Advanced Institute of Nanotechnology

(SAINT), Department of Physics, Sungkyunkwan University,

Suwon, 16419, Republic of Korea

Department of Chemistry, SRM Institute of Science and

Technology, Kattankulathur, 603203, India

Department of Polymer Science and Engineering,

Department of IT Convergence (BK21 PLUS) Chemical

Industry Institute, Korea National University of

Transportation, Chungju, 27469, Republic of Korea

Department of Information and Communications, Jongbu

University 305 Donghen-ro, Goyang, Kyunggi-do, 10279,

Republic of Korea

Current Applied Physics

https://doi.org/10.1016/j.cap.2019.05.008

Although metal nanoparticles (NPs) have been widely

reported, Au NPs functionalized reduced graphene

oxide (rGO)/GaN nanorods (NRs) for multi-functional

applications are rarely discussed. The rGO is a well

known transparent electrode and has been

considering an alternative electrode to ITO in the

current optoelectronic community. In this work, Au

NPs functionalized rGO (Au@rGO)/GaN NRs hybrid

structure probed for photodetector and CO gas

sensing applications. The hybrid structure was

characterized by scanning electron microscopy,

transmission electron microscope, current-voltage

characteristics, photo conductivity, and gas sensor

measurements. The Au@rGO/GaN NRs showed

higher photoresponsivity (λ = 382 nm, 516 nm)

compared to rGO/GaN NRs at room temperature. The

rising and falling times of Au@rGO/GaN NRs are

faster than that of rGO/GaN NRs. The hybrid

structure Au@rGO/GaN NRs exhibited high CO gas

response compared to rGO/GaN NRs at room

temperature (∼38% to the 20 ppm). Au NPs played

an important role in terms of electronic and chemical

changes in the hybrid structure for improving both

photodetectors the CO gas response. Such a multi-


https://doi.org/10.1016/j.cap.2019.05.008


functional hybrid device is an interest of various

room temperature applications.

Visible- and solar-blind photodetectors using AlGaN

high electron mobility transistors with a nanodot-

based floating gate Sandia National Laboratories, Albuquerque, New Mexico

87185, USA

Sandia National Laboratories, Livermore, California 94550,

USA

Photonics Research


AlGaN-channel high electron mobility transistors

(HEMTs) were operated as visible- and solar-blind

photodetectors by using GaN nanodots as an

optically active floating gate. The effect of the

floating gate was large enough to switch an HEMT

from the off-state in the dark to an on-state under

illumination. This opto-electronic response achieved

responsivity >108 A/W at room temperature while

allowing HEMTs to be electrically biased in the off-

state for low dark current and low DC power

dissipation. The influence of GaN nanodot distance

from the HEMT channel on the dynamic range of the

photodetector was investigated, along with the

responsivity and temporal response of the floating

gate HEMT as a function of optical intensity. The

absorption threshold was shown to be controlled by

the AlN mole fraction of the HEMT channel layer,

thus enabling the same device design to be tuned for

either visible- or solar-blind detection.

Long‐Term, High‐Voltage, and High‐Temperature

Stable Dual‐Mode, Low Dark Current Broadband

Ultraviolet Photodetector Based on Solution‐Cast

r‐GO on MBE‐Grown Highly Resistive GaN CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road,

New Delhi 110012, India

Academy of Scientific and Innovative Research (AcSIR),

CSIR-HRDC Campus, Ghaziabad 201002, India

Surface Physics and Material Science Division, Saha

Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata

700064, India

Advanced Optical Materials

https://doi.org/10.1002/adom.201900340

New generation of hybrid photodetectors may

provide the optimal solution for compact, highly

sensitive, durable, and reliable broadband ultraviolet

(BUV) sensors. A high‐performance dual‐mode BUV

photodetector based on melding of highly resistive

GaN and reduced graphene oxide is reported. Under

zero bias, the device exhibits a sub‐picoampere dark

current, high light‐to‐dark current (ILight/IDark) ratio

of ≈3.8 × 103 and high BUV–visible rejection ratio

(≈1.8 × 102) with fast rise and fall times. The

photodetector displays remarkable stability when

subject to extreme operating conditions. The

photoresponse of the detector shows a dark current

of ≈2.41 nA at ± 200 V bias, ILight/IDark ratio of ≈200

and high BUV–vis rejection ratio (≈7 × 102). The

response time of device is typically in the range of

15–27 ms measured at 12 Hz light chopping

frequency. When subjected to high working

temperature of up to 116 °C, it shows a stable optical

switching response. In addition, the device displays

impressive long‐term stability with no change in

photoresponse even after a period of 28 months. This

unique combination of low dark current, dual‐mode

operation, and no aging effects upon prolonged

exposure to high‐operating voltage,

high‐temperature, and BUV radiation is attractive for

a variety of harsh environment applications.

Nanowire photodetectors based on wurtzite

semiconductor heterostructures Univ. Grenoble-Alpes, CNRS, Institut Néel, 25 av. des


Univ. Grenoble-Alpes, CEA, IRIG-PHELIQS, 17 av. des


Semiconductor Science and Technology

https://doi.org/10.1088/1361-6641/ab0cb8

Using nanowires for photodetection constitutes an

opportunity to enhance the absorption efficiency

while reducing the electrical cross-section of the

device. Nanowires present interesting features like

compatibility with silicon substrates, which offers the

possibility of integrating detector and readout

circuitry and facilitates their transfer to flexible

substrates. The incorporation of heterostructures in

nanowire photodetectors opens interesting prospects

for application and performance improvement.

Within a nanowire, it is possible to implement axial


https://doi.org/10.1002/adom.201900340



and radial (core-shell) heterostructures, and these

two types can be combined to obtain the three-

dimensional carrier confinement (dot-in-a-wire)

which is required for the development of quantum

photodetectors. If the nanowires present wurtzite

crystallographic structure, the presence of

heterointerfaces can induce internal electric fields

due to the difference of polarization between the

constituents. Such polarization-induced internal

electric fields, like those induced by heterojunctions

or type-II heterostructures, can be ingeneered to

favor the separation of the photogenerated electrons

and holes. This paper provides a general review of

latest progresses in nanowire photodetectors,

including single nanowires and heterostructured

nanowires.

Highly sensitive AlGaN/GaN HEMT biosensors using

an ethanolamine modification strategy for bioassay

applications School of Nano Technology and Nano Bionics, University of


i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics,

Chinese Academy of Sciences, Suzhou 215125, People's

Republic of China

Key Laboratory of Multifunctional Nanomaterials and

Smart Systems, Chinese Academy of Sciences, Suzhou

215125, People's Republic of China

The College of Materials Sciences and Engineering,

Shanghai University, Shanghai 200444, China

The College of Nuclear Technology and Automation

Engineering, Chengdu University of Technology, Chengdu

610059, China

RSC Advances

https://doi.org/10.1039/C9RA02055A

In this paper, we propose a highly efficient surface

modification strategy on an AlGaN/GaN high electron

mobility transistor (HEMT), where ethanolamine (EA)

was utilized to functionalize the surface of GaN and

provided amphoteric amine groups for probe

molecular immobilization for bioassay application.

The molecular gated-AlGaN/GaN HEMT was utilized

for pH and prostate-specific antigen (PSA) detection

to verify its performance as a biosensor. Benefitting

from the high coating quality on the GaN surface, the

performance of our biosensor is drastically improved

compared to other AlGaN/GaN HEMT based pH and

PSA biosensors reported before. Our molecular

gated-AlGaN/GaN HEMT biosensor has achieved

good static electrical performance for pH sensing,

such as high sensitivity, good linearity and chemical

stability. Moreover, after further immobilization of

PSA antibody onto the EA aminated GaN surface, the

limit of detection (LOD) for PSA detection is as low as

1 fg mL−1 in PBS buffer, which has reached an at least

two orders of magnitude decrease compared to any

other AlGaN/GaN HEMT based PSA biosensor

reported before. And the sensitivity of our PSA

biosensor has achieved a substantial increase,

reaching up to 2.04% for 100 ng mL−1. The

measurements of pH and PSA utilizing the EA

modified AlGaN/GaN HEMT biosensor indicate that

the surface modification strategy on the GaN

proposed in this paper can effectively improve the

performance of the AlGaN/GaN HEMT based

biosensor, which demonstrates a promising

application prospect in the AlGaN/GaN HEMT based

biological detection field.

Design and fabrication of AlGaN/GaN high electron

mobility transistors for biosensing applications Department of Electronics and Communication

Engineering, Malaviya National Institute of Technology,

Jaipur, India

CSI Transactions on ICT

https://doi.org/10.1007/s40012-019-00233-y

Developing and optimizing FET platforms for label

free bio molecule detection has gained huge interest

in recent years. This paper presents a charge control

model based sensitivity analysis of an optimized GaN

HEMT for pH and biomarker detection. Analytical

modeling, simulation and fabrication of the device

have been discussed in this paper with focus on its

sensing application. The overall aim is to enhance the

sensitivity of AlGaN/GaN HEMT by epitaxial

optimization and contact optimizations and deliver a

highly efficient end product with desired sensitivity

for bio/chemical detection.


https://doi.org/10.1007/s40012-019-00233-y


GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)

Information selected by Knowmade

Significant Phonon Drag Enables High Power Factor

in the AlGaN/GaN Two-Dimensional Electron Gas Department of Mechanical Engineering, Stanford

University, Stanford, CA 94305, USA.

Department of Electrical Engineering, Stanford University,

Stanford, CA 94305, USA.

Department of Thermal and Fluid Engineering, University

of Twente, Enschede, 7500 AE, Netherlands.

Department of Materials Science and Engineering, UC

Berkeley, CA 94720, USA.

Department of Applied Physics, Stanford University,


Stanford Institute for Materials and Energy Sciences, SLAC

National Accelerator Laboratory, Menlo Park, CA 94025,

USA.

Department of Physics, Stanford University, Stanford, CA

94305, USA.

Department of Materials Science and Engineering,

Stanford University, Stanford, CA 94305, USA.

Precourt Institute for Energy, Stanford University,


Department of Aeronautics and Astronautics, Stanford

University, Stanford, CA 94305, USA.

NanoLetters

https://doi.org/10.1021/acs.nanolett.9b00901

In typical thermoelectric energy harvesters and

sensors, the Seebeck effect is caused by diffusion of

electrons or holes in a temperature gradient.

However, the Seebeck effect can also have a phonon

drag component, due to momentum exchange

between charge carriers and lattice phonons, which is

more difficult to quantify. Here, we present the first

study of phonon drag in the AlGaN/GaN two-

dimensional electron gas (2DEG). We find that

phonon drag does not contribute significantly to the

thermoelectric behavior of devices with ∼100 nm

GaN thickness, which suppresses the phonon mean

free path. However, when the thickness is increased

to ∼1.2 μm, up to 32% (88%) of the Seebeck

coefficient at 300 K (50 K) can be attributed to the

drag component. In turn, the phonon drag enables

state-of-the-art thermoelectric power factor in the

thicker GaN film, up to ∼40 mW m–1 K–2 at 50 K. By

measuring the thermal conductivity of these

AlGaN/GaN films, we show that the magnitude of the

phonon drag can increase even when the thermal

conductivity decreases. Decoupling of thermal

conductivity and Seebeck coefficient could enable

important advancements in thermoelectric power

conversion with devices based on 2DEGs.

Simulation study for the current matching

optimization in In0.48Ga0.52N/In0.74Ga0.26N dual

junction solar cells Laboratory of Metallic and Semiconductor Materials,

University of Biskra, Algeria

Faculty of Science, University of Batna, Algeria

DIIES – Mediterranea University of Reggio Calabria, Italy



In this paper indium gallium nitride (InGaN) is used to

design and optimize a dual junction (DJ) solar cell,

which is series-connected via a tunnel diode, with a

careful analysis of the current matching between the

top and the bottom sub-cells. In particular, a bandgap

combination of 1.76eV/1.13eV for an

In0.48Ga0.52N/In0.74Ga0.26N structure is adopted

and several numerical simulation results are

presented. The doping concentration and the base

thickness of each sub-cell are considered as fitting

parameters in order to determine an accurate

current matching condition. The In0.48Ga0.52N-

based n++/p++ tunnel junction behavior is also taken

into account. A maximum short circuit current

density of 19.543 mA/cm2 is obtained for a 1 μm-

thick base in both the sub-cells, and a p/n doping

ratio of 5 × 1018 cm−3/5 × 1015 cm−3 and

1.9 × 1019 cm−3/1.9 × 1016 cm−3 for the top and the

bottom cell, respectively. The optimized DJ solar cell

exhibits an open circuit voltage of 1.713 V, a fill factor

of 82.49%, and a conversion efficiency of 28.78%. The

external quantum efficiency and the current (power)

density-voltage characteristics of different devices

are investigated in detail.

https://doi.org/10.1021/acs.nanolett.9b00901



A theoretical investigation of pyroelectric effect and

thermoelectric improvement of AlInN/GaN

heterostructures Department of Physics, N.I.T, Raipur, Raipur 492010, India

Thin Solid Films


Improved thermoelectric (TE) efficiency of AlxIn1-

xN/GaN heterostructure (HS) requires high Seebeck

coefficient (S) and electrical conductivity (σ); but

small thermal conductivity (k). Built-in polarization

(BIP) electric field of AlxIn1-xN/GaN HS enhances S

and σ. In this work theoretically BIP effect on k of HS

is explored. It is found that thermal conductivities k

and kp (in absence and presence of BIP, respectively)

vs temperature show a crossover at a temperature

Tp. Below Tp, kp is lower than k due to negative

thermal expansion causing dominance of

spontaneous polarization (sp) over piezoelectric

polarization (pz); while above Tp, kp is higher than k

due to positive thermal expansion causing dominance

of pz over sp. This change in polarization with

temperature signifies poyroelectric behavior with Tp

as transition temperature between primary and

secondary pyroelectricity because above Tp thermal

expansion takes place which is reason of secondary

pyroelectricity. For x = 0.1, 0.2, 0.4 and 0.5, Tp are

close to 200, 210, 300 and 360 K, respectively. Tp can

be raised above room temperature by changing x and

interfacial strain judiciously. Theoretical findings are

made comparisons with results available in the

current literature. Thus, TE efficiency of HS is

improved by polarization field below Tp; making it

suitable simultaneously for pyroelectric sensors and

TE module for maximum power production.

Intrinsic properties of macroscopically tuned gallium

nitride single crystalline facets for electrocatalytic

hydrogen evolution State Key Lab of Crystal Materials, Shandong University,

Jinan, 250100, P. R. China.

Chemistry, A European Journal

https://doi.org/10.1002/chem.201901395

The anisotropy of crystal materials results in different

physical and chemical properties on their different

facets, warranting an in‐depth investigation.

Macroscopically facet‐tuned, high‐purity gallium

nitride (GaN) single crystals were synthesised and

machined, and electrocatalytic hydrogen evolution

reaction (HER) was set as the template reaction to

show the differences among the facets. The density

functional theory (DFT) calculation revealed that the

Ga and N sites of GaN (100) had a considerably

smaller ΔGH* value than the metal Ga site of GaN

(001) or N site of GaN (00‐1), thereby indicating that

GaN (100) should be more catalytically active for HER

on account of its nonpolar facet. The subsequent

experiments testified that the electrocatalytic

performance of GaN (100) was considerably more

efficient than that of other facets for both acidic and

alkaline HERs. Moreover, the GaN crystal with a

preferentially (100) active facet possessed an

excellently durable alkaline electrocatalytic HER for

more than 10 days. This work provides fundamental

insights into the exploration of the intrinsic

properties of materials and designing advanced

materials for physicochemical applications.

Stable Unassisted Solar Water Splitting on

Semiconductor Photocathodes Protected by Multi-

Functional GaN Nanostructures Department of Electrical Engineering and Computer

Science, University of Michigan, 1301 Beal Avenue, Ann

Arbor, Michigan 48109, USA

Department of Materials Science and Engineering,

University of Michigan, 2300 Hayward Street, Ann Arbor,

Michigan 48109, USA

ACS Energy Lett.

https://doi.org/10.1021/acsenergylett.9b00549

Producing hydrogen by unassisted solar water

splitting is one essential step to make direct solar fuel

conversion a viable energy source. To date, however,

there has been no demonstration of stable

photoelectrodes for high efficiency

photoelectrochemical water splitting. In this work,

we report that a GaInP2/GaAs/Ge triple-junction (3J)

photocathode protected by multi-functional GaN

nanostructures can enable both efficient and

relatively stable solar water splitting. A 12.6% solar-

to-hydrogen (STH) efficiency is measured without any

external bias. Of particular importance, we

demonstrate relatively stable solar water splitting for

80 hours in three-electrode configuration and 57


https://doi.org/10.1002/chem.201901395

https://doi.org/10.1021/acsenergylett.9b00549


hours in two-electrode measurement at zero bias.

This is the best reported stability for multi-junction

semiconductor photocathodes in two-electrode

configuration to our knowledge. The multifunctional

GaN nanostructure significantly reduces the charge

transfer resistance at semiconductor/electrolyte

interface and protects III-V materials against

corrosion. Such multi-functional GaN photocatalytic

nanostructures provide a new pathway to improve

the performance of conventional photoelectrodes to

achieve both efficient and stable unassisted solar

water splitting.

Photoluminescence of CuInSe2/GaN and

CuInSe2/InN Department of Physics, National Sun Yat-Sen University,

Kaohsiung, 80424, Taiwan, ROC

Institute of Mathematical Sciences and Physics, University

of the Philippines Los Baños, Laguna, 4031, Philippines

Department of Physics, Tamkang University, New Taipei

City, 25137, Taiwan, ROC

Journal of Luminescence

https://doi.org/10.1016/j.jlumin.2019.05.018

The power and temperature dependent

photoluminescence (PL) of epitaxially grown In-rich

CuInSe2 (CIS) and Cu-rich CIS deposited on N-polar

GaN and InN were investigated in this paper. The In-

rich CIS/GaN has two PL emissions characterized by a

donor-acceptor pair (DAP) peak at 0.92 eV and an

excitonic peak at 1.08/1.1 eV. On the other hand, the

Cu-rich CIS/GaN has four PL emissions characterized

by two DAP peaks at 0.86 eV and 0.94 eV, free-to-

bound recombination peak at 0.97 eV and an

excitonic peak at 1.03 eV. Identification of these

defects in the CIS absorber layer is crucial for the

improvement of the device efficiency. The PL

emission of the CIS/InN closely resembles that of the

Cu-rich CIS/GaN. For all the samples, the PL intensity

increased with excitation power while the PL

intensity decreased with temperature. The obtained

power coefficients and activation energies support

the proposed mechanism causing the luminescence.

The defects present in CIS/GaN and CIS/InN were also

identified. The results from this study are consistent

with those of CIS single crystals and show that the CIS

absorber layer can be incorporated with III-nitride

materials, and its absorption can be extended beyond

the spectrum covered by plain CIS.

Analysis of the performance of InxGa1−xN based

solar cells Nanoscience and Nanotechnology Doctoral Program,

CINVESTAV-IPN, Mexico City, Mexico

Electrical Engineering Department SEES, CINVESTAV-IPN,

Mexico City, Mexico

Mathematics and Physics Department, ITESO,

Tlaquepaque, Mexico

ESFM, Instituto Politécnico Nacional, Mexico City, Mexico

Physics Department, CINVESTAV-IPN, Mexico City, Mexico

SN Applied Sciences

https://doi.org/10.1007/s42452-019-0650-x

We have modeled InxGa1−xN single homo-junction

solar cells considering realistic carrier transport

parameters. It is shown that the maximum efficiency

will be less than 19% for an Indium content around

60%. This practical efficiency limit is due to

technological issues such as the residual high electron

background making it difficult to have p-type doping,

causing a low open circuit-voltage and the reduction

of the absorber depletion region, and as a result a

drop in the photo-current generation. Besides, the

difficulty for incorporating In concentrations higher

than 40% without phase separation in addition to

highly defective material should also be considered.

The model does not take in account the carrier

lifetime variation as a function of the In content

because there are no experimental studies about this

yet. To overcome this lack of knowledge, the solar

cell with the highest possible In content was modeled

by varying the carrier lifetimes from picoseconds to

nanoseconds giving calculated efficiencies in the

range from 3.9 to 18.9%, respectively. These results

explain the poor experimental efficiencies already

reported for InxGa1−xN single homo-junction solar

cells and suggest that, even in the best case, the

expected efficiency will be below that obtained for

more conventional Si and GaAs solar cells. Hence, our

analysis indicates that alternative ways, such as using

nanoparticles or nanowires engineered for making

competitive solar cells using this kind of materials,

should be looked for in the near future.

https://doi.org/10.1016/j.jlumin.2019.05.018

https://doi.org/10.1007/s42452-019-0650-x


Improvement in carrier dynamics in InxGa1−xN/GaN

multi-quantum well for solar cell applications Faculty of Technology, University of Blida 1, Blida, Algeria

Institute of Electronics, Microelectronics and

Nanotechnology (IEMN), UMR CNRS 8520, University of

Sciences and Technologies of Lille 1, Villeneuve of Ascq,

France

Journal of Optics

https://doi.org/10.1007/s12596-019-00536-y

In this work, we have studied and simulated

nanostructures to improve the solar cell efficiency.

The idea of this study is to insert multi-quantum wells

in the structure of a solar cell (MQWSC). The electric

field, recombination, and the photogeneration rates

of charge carriers in QWSC influence the collection

and carrier extraction efficiency. In this work, the

behavior of these magnitudes and the main

characteristics as current density–voltage J–V and

external quantum efficiency of In0.35Ga0.65N/GaN

MQWSC are studied. Our results have shown that the

insertion of five MQW layers within the intrinsic

region of p-GaN/i-InGaN/n-GaN heterojunction solar

cell can increase both short-circuit current and the

conversion efficiency from 0.89 to 2.12 mA/cm2 and

0.78 to 1.25%, respectively; additionally, with the

same number of embedded MQWs, the absorption

range edge of the heterojunction solar cell extends

from 430 to 500 nm.

Enhanced water splitting performance of GaN

nanowires fabricated using anode aluminum oxide

templates State Key Laboratory on Integrated Optoelectronics,

Institute of Semiconductors, Chinese Academy of Sciences,

P. R. China

Semiconductor Lighting Research and Development

Center, Institute of Semiconductors, Chinese Academy of

Sciences, P. R. China

College of Materials Science and Optoelectronic

Technology, University of Chinese Academy of Sciences,

Beijing 100049, People's Republic of China

RSC Advances


Highly ordered GaN nanowires were fabricated using

an anodic aluminum oxide (AAO) template.

Compared to planar GaN, the GaN nanowires

significantly increased the light absorption, and the

saturated photocurrent increased by a factor of 5

from 0.075 to 0.38 mA cm−2. The photocurrent

increase with the GaN nanowires is not only due to

their increased surface to volume ratio and reduction

in the distance for photo-generated carriers to reach

the electrolyte, but also the built-in electric field,

which mainly contribute to the enhancement in their

water splitting ability. The GaN nanowires can lead to

band bending due to their surface states and the

formation of a polarized electric field to accelerate

the separation of photo-generated carriers. We also

established a theoretic model to simulate the band

bending in the nanowires. The results showed that

when the nanowire diameters are equal or bigger

than the full width of depletion region, the nanowires

have the maximum electric field, which improves

their water splitting performance significantly. These

results provide a cost-effective way for highly

efficient water splitting.

Reconsideration of the gallium nitride: Dual

functionality as an electron transporter and

transparent conductor for recyclable polymer solar

cell substrate applications Department of Molecular Science and Technology, Ajou

University, Suwon, 16499, Republic of Korea

LED R&D Division, Korea Photonics Technology Institute,

Gwangju, 500-779, Republic of Korea

Department of Energy systems, Soonchunhyang University,

Asan, 31583, Republic of Korea

Australian Centre for Advanced Photovoltaics (ACAP),

School of Photovoltaic and Renewable and Engineering,

University of New South Wales, Sydney, 2052, Australia

Surface Technology Division, Korea Institute of Materials

Science (KIMS), 797 Changwondaero, Sangsan-Gu,

Changwon, Gyeongnam, 642-831, Republic of Korea

Solar Energy Materials and Solar Cells

https://doi.org/10.1016/j.solmat.2019.109971

Herein, we report the dual functionality of a single n-

type gallium nitride (n-GaN) layer as an electron

transporter and transparent conductor, which has

applications in reusable organic solar cells. After

silicon doping with an optimized electron

concentration, thin-film layer of GaN showed

exceptional electrical properties including charge

carrier mobility of 161 cm2 V−1s−1, electrical

https://doi.org/10.1007/s12596-019-00536-y


https://doi.org/10.1016/j.solmat.2019.109971


conductivity of 1.4ⅹ106 S cm−1, and sheet

resistance of 11.1 Ω cm−2. Organic solar cells based

on n-GaN exhibited power conversion efficiency

comparable to those based on a conventional

ITO/ZnO bilayered cathode. Furthermore, the n-GaN

substrates exhibited reusability; due to excellent

chemical stability of n-GaN, the reconstructed organic

solar cells maintained their initial performance after

the substrates were recycled. We suggest a new type

of reusable n-GaN cathode layer featuring an

integrated electron transporting layer and

transparent electrode.


GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)

NANO

Information selected by Jesús Zúñiga Pérez (CRHEA-CNRS)

Vertical GaN Nanowires and Nanoscale Light-

Emitting-Diode Arrays for Lighting and Sensing

Applications Institute of Semiconductor Technology (IHT), TU

Braunschweig, 38106 Braunschweig, Germany

Laboratory for Emerging Nanometrology (LENA), TU

Braunschweig, 38106 Braunschweig, Germany;

Research Center for Physics, Indonesian Institute of

Sciences (LIPI), 15314 Tangerang Selatan, Indonesia

MIND-IN2 UB, Department of Engineering - Electronics,

University of Barcelona, 08028 Barcelona, Spain.

ACS Appl. Nano Mater.

https://doi.org/10.1021/acsanm.9b00587

For various lighting and monolithic sensor systems

applications, vertically aligned three dimensional

(3D) gallium nitride (GaN) and InGaN/GaN-based

LED nanowire arrays with sub-200 nm feature sizes

(down to 35 nm) were fabricated using nanosphere

lift-off lithography (NSLL) technique combined with

hybrid top-down etching (i.e., inductively coupled

plasma dry reactive ion etching (ICP-DRIE) and wet

chemical etching). Owing to the lithographic

opening and well-controlled surface

functionalization prior to the polystyrene

nanosphere (PN) deposition, vertical GaN nanowire

arrays with an area density of 9.74 × 108 cm-2 and

an aspect ratio of >10 could be realized in a

specified large area of 1.5 × 1.5 mm2. Optoelectrical

characteristics of the nanoLEDs were further

investigated in cathodoluminescence (CL)

measurements, in which the multi-quantum well

(MQW) shows a clear CL-emission at a wavelength

of 465 nm. Thus, using NSLL to manufacture low-

cost but highly ordered 3D GaN-based nanowires

and nanoLEDs is a feasible alternative to other

sophisticated but more expensive nanolithography

methods.

Influence of surface nitridation and an AlN buffer

layer on the growth of GaN nanostructures on a

flexible Ti metal foil using laser molecular beam

epitaxy CSIR-National Physical Laboratory, Dr. K.S. Krishnan

Marg, New Delhi 110012, India

Academy of Scientific and Innovative Research (AcSIR),

Ghaziabad 201002, India


https://doi.org/10.7567/1347-4065/ab0f17

GaN nanorods (NRs) and hollow nanocolumns

(HNCs) were grown on flexible Ti foils using laser-

assisted molecular beam epitaxy at a growth

temperature of 700 °C. The shape, size and density

of the GaN nanostructures were tuned by surface

nitridation and AlN buffer layer growth

temperature on a Ti foil. Sparse (~ 5.5 × 108 cm−2)

GaN NRs were obtained on the bare surface

whereas dense (~3.47 × 109 cm−2) GaN NRs were

grown on the nitridated Ti foil. The shape of the

GaN changed from NRs to HNCs by introducing an

AlN buffer layer on nitridated Ti foil. Raman

spectroscopy showed the grown GaN

nanostructures have a wurtzite crystal structure.

Room-temperature photoluminescence

spectroscopy measurements show that the GaN

nanostructures possess an intensive near band edge

emission at ~3.42 eV with a negligible defect-

related peak. The growth of tunable GaN

nanostructures on flexible metal foils is attractive

for flexible optoelectronics and sensor devices.

Nanowire photodetectors based on wurtzite

semiconductor heterostructures Univ. Grenoble-Alpes, CNRS, Institut Néel, 25 av. des


Univ. Grenoble-Alpes, CEA, IRIG-PHELIQS, 17 av. des


Semiconductor Science and Technology


Using nanowires for photodetection constitutes an

opportunity to enhance the absorption efficiency

https://doi.org/10.1021/acsanm.9b00587

https://doi.org/10.7567/1347-4065/ab0f17



while reducing the electrical cross-section of the

device. Nanowires present interesting features like

compatibility with silicon substrates, which offers

the possibility of integrating detector and readout

circuitry and facilitates their transfer to flexible

substrates. The incorporation of heterostructures in

nanowire photodetectors opens interesting

prospects for application and performance

improvement. Within a nanowire, it is possible to

implement axial and radial (core-shell)

heterostructures, and these two types can be

combined to obtain the three-dimensional carrier

confinement (dot-in-a-wire) which is required for

the development of quantum photodetectors. If the

nanowires present wurtzite crystallographic

structure, the presence of heterointerfaces can

induce internal electric fields due to the difference

of polarization between the constituents. Such

polarization-induced internal electric fields, like

those induced by heterojunctions or type-II

heterostructures, can be ingeneered to favor the

separation of the photogenerated electrons and

holes. This paper provides a general review of latest

progresses in nanowire photodetectors, including

single nanowires and heterostructured nanowires.

Optical Performance of Top-Down Fabricated

AlGaN Nanorod Arrays with Multi-Quantum Wells

Embedded Department of Physics, Fujian Key Laboratory of

Semiconductor Materials and Applications, Collaborative

Innovation Center for Optoelectronic Semiconductors

and Efficient Devices, Xiamen University, Xiamen, China

Jiangsu Provincial Key Laboratory of Advanced Photonic

and Electronic Materials, School of Electronic Science

and Engineering, Nanjing University, Nanjing, China

Nanoscale Research Letters

https://doi.org/10.1186/s11671-019-3003-1

Deep ultraviolet AlGaN-based nanorod (NR) arrays

were fabricated by nanoimprint lithography and

top-down dry etching techniques from a fully

structural LED wafer. Highly ordered periodic

structural properties and morphology were

confirmed by scanning electron microscopy and

transmission electron microscopy. Compared with

planar samples, cathodoluminescence

measurement revealed that NR samples showed

1.92-fold light extraction efficiency (LEE)

enhancement and a 12.2-fold internal quantum

efficiency (IQE) enhancement for the emission from

multi-quantum wells at approximately 277 nm. The

LEE enhancement can be attributed to the well-

fabricated nanostructured interface between the

air and the epilayers. Moreover, the reduced

quantum-confined stark effect accounted for the

great enhancement in IQE.

A p-Channel GaN Heterostructure Tunnel FET with

High ON/OFF Current Ratio Department of Electronic and Electrical Engineering, The

University of Sheffield, Sheffield S3 7HQ, U.K..


https://doi.org/10.1109/TED.2019.2915768

A novel mechanism to achieve a nonambipolar

tunnel FET (TFET) is proposed in this paper. The

method relies on polarization charge induced in

semiconductors, such as group III nitrides, to

enhance the electric field across the junction and

facilitate unidirectional tunneling based on the

polarity of the applied gate bias. This also enables

enhanced control over the tunneling distance,

reducing it significantly in comparison to a

conventional TFET. The proposed p-channel device

implemented in a novel vertical GaN nanowire

geometry facilitates a reduction of footprint while

still maintaining comparable performance to that of

conventional E-mode p-channel devices in GaN. This

opens up possibilities for E-mode p-channel GaN

devices.

NON/SEMI POLAR Information selected by

Knowmade Enhanced hole concentration and improved

surface morphology for nonpolar a-plane p-type

AlGaN/GaN superlattices grown with indium-

surfactant Advanced Photonics Center, Southeast University,

Nanjing, 210096, Jiangsu, China



The nonpolar a-plane Mg-delta-doped

Al0.6Ga0.4N/GaN superlattices (SLs) with enhanced

https://doi.org/10.1186/s11671-019-3003-1

https://doi.org/10.1109/TED.2019.2915768



hole concentration were successfully grown by

using indium (In)-surfactant with metal organic

chemical vapor deposition (MOCVD) technology.

The effect of In-surfactant on the characteristics of

the nonpolar a-plane Mg-doped AlGaN/GaN SLs

were studied with scanning electron microscopy,

atomic force microscopy, X-ray diffraction, and Hall

effect measurements. It was found that the surface

morphology was improved evidently and the hole

concentration was enhanced effectively with the

use of In-surfactant. In fact, a root-mean-square

value as small as 0.8 nm and a hole concentration

as high as 5.1 × 1017 cm-3 were achieved by

carefully optimizing the TMIn mole flow rate in the

MOCVD growth process. Moreover, it was inferred

that the enhancement in hole concentration was

due to the significant increase in the Mg

incorporation efficiency and the decrease in the

self-compensation effect induced by the proper

usage of In-surfactant.

Improved crystal quality of nonpolar a-plane GaN

based on the nano pattern formed by the

annealed thin Ni layer Wide Bandgap Semiconductor Technology Disciplines

State Key Laboratory, School of Microelectronics, Xidian

University, Xi'an, 710071, China



A method to improve the nonpolar (11–20) a-plane

GaN crystalline quality is investigated. The

promoted crystal quality of a-plane GaN is achieved

through growing on the a-plane GaN template with

nano pattern. For on-axis (11–20) plane X-ray

rocking curves, the full width at half maximum

values are remarkably reduced from 2834 to 1210

arcsec, 2868 to 780 arcsec along the m-axis and the

c-axis directions, respectively. Also, the improved

crystalline quality results in the better optical

properties according to the photoluminescence and

Raman measurements. Moreover, the cross-

sectional transmission electron microscopy is also

used to study the mechanisms of dislocation

reduction. Evidently, this technique is effective in

promoting crystal quality of nonpolar a-plane GaN.

Microscopic analysis of interface composition

dynamics in m-plane AlInN Institute of Applied Physics, Technische Universität

Braunschweig, Mendelssohnstraße 2, 38106

Braunschweig, Germany

Laboratory for Emerging Nanometrology, Braunschweig,

Germany

Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG

Eindhoven, The Netherlands


https://doi.org/10.7567/1347-4065/ab079d

We present first microscopic evidence on

approximately two monolayers of interfacial indium

depletion in one-directionally lattice-matched AlInN

grown on m-plane GaN as measured by energy

dispersive X-ray spectroscopy. Contrary to other

reports, we find no significant incorporation of

parasitic gallium into the volume material, but only

some spreading of gallium across the GaN/AlInN

heterointerface. Using a quantitative description of

this behaviour, we conclude that the observed

effects are not depending on the crystal

orientation, nominal stoichiometry and strain state

of the AlInN, but rather represent an inherent

characteristic of its growth dynamics, related to the

differences in metal-nitrogen binding energies of

AlN and InN.

Magnetic-induced PL modulation of InGaN/GaN

MQWs by a CoFeB ferromagnetic cap layer Beijing Key Laboratory for Magneto-Photoelectrical

Composite and Interface Science, School of Mathematics

and Physics, University of Science and Technology

Beijing, No. 30, Xueyuan Road, Beijing 100083, People's

Republic of China


https://doi.org/10.7567/1347-4065/ab0cfe

III-nitride semiconductors show wide applications in

general illumination, displays, visible-light

communication, power electronics and so on. Until

recently, it has been rather hard to experimentally

realize magnetic modulation or coupling due to the

lack of magnetism in GaN-based semiconductors.

Here, we have fabricated the nonpolar a-plane

InGaN/GaN MQWs capped by ferromagnetic CoFeB

thin film. After magnetizing a CoFeB cap layer under


https://doi.org/10.7567/1347-4065/ab079d

https://doi.org/10.7567/1347-4065/ab0cfe


a low magnetic field of 100 mT, the peak PL

wavelength of nonpolar a-plane InGaN/GaN MQWs

has a red shift from 460 to 475 nm, while its PL

polarization degree shows an effective

enhancement from 29% to 41% by increasing the

CoFeB thickness. The magnetic-induced carrier

redistribution has played a great role on the PL

modulation of nonpolar InGaN/GaN MQW active

region. Therefore, our proposed method exhibits a

great potential to develop the highly polarized light

emitters, optical polarization modulation,

polarization-sensitive detectors, magnetic-optical

modulation and coupling sensing in future multi-

field applications.

Ultrafast carrier dynamics of conformally grown

semi-polar (11[2 with combining macron]2)

GaN/InGaN multiple quantum well co-axial

nanowires on m-axial GaN core nanowires Department of Physics, Chonnam National University,

Gwangju 61186, Republic of Korea

Department of Physics and KI for the NanoCentury,

Korea Advanced Institute of Science and Technology,

Daejeon 34141, Republic of Korea

Optoelectronics Convergence Research Center, Chonnam

National University, Gwangju 61186, Republic of Korea

Nanoscale

https://doi.org/10.1039/C9NR02823D

The growth of semi-polar (11[2 with combining

macron]2) GaN/InGaN multiple-quantum-well

(MQW) co-axial heterostructure shells around m-

axial GaN core nanowires on a Si substrate using

MOCVD is reported for the first time. The core GaN

nanowire and GaN/InGaN MQW shells are grown in

a two-step growth sequence of vapor–liquid–solid

and vapor–solid growth modes. The luminescence

and carrier dynamics of GaN/InGaN MQW coaxial

nanowires are studied by photoluminescence,

cathodoluminescence, and low temperature time-

resolved photoluminescence (TRPL). The emission is

tuned from 430 nm to 590 nm by increasing the

InGaN QW thickness. The non-single exponential

decay measured by low-temperature TRPL was

attributed to the indium fluctuations in the InGaN

QW. The ultrafast radiative lifetime was measured

from 14 ps to 26 ps with different emission

wavelengths at a very high internal quantum

efficiency up to 68%. An ultrafast carrier lifetime

was assigned to the growth of the InGaN QW on

semi-polar (11[2 with combining macron]2) growth

facet and the improved carrier collection efficiency

due to the radial growth of the GaN/InGaN MQW

shells. Such an ultrafast carrier dynamics of NWs

provides a meaningful active medium for high

speed optoelectronic applications.

Controlling the orientations of directional

sputtered non- and semi-polar GaN/AlN layers Department of Electronics, Nagoya University, Furo-cho,

Chikusa-ku, Nagoya 464-8603, Japan

Institute of Materials and Systems for Sustainability,

Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-

8601, Japan

Akasaki research center, Nagoya University, Furo-cho,

Chikusa-ku, Nagoya 464-8603, Japan


https://doi.org/10.7567/1347-4065/ab1252

We have studied the impact on the surface

orientation of different sputtered Al layers followed

by AlN layers sputtered on m-plane sapphire. These

initial layers were then overgrown by AlN and

followed by GaN using metal-organic vapor phase

epitaxy (MOVPE). By increasing sputtering time of

the initial Al layer from 0 s to 15 s, we obtained

single phase (10-10), (10-13) and (10-14) GaN/AlN

layers. The thickness of the initial Al layer was

estimated by optical transmission measurements to

be about 0.5–1 nm for the (10-13) orientation, and

>1 nm for the (10-14) orientation. After MOVPE

growth, no trace of metallic Al was found by

transmission electron microscopy, indicating that

this layer was fully converted to AlN.

Reduced radiative emission for wide nonpolar III-

nitride quantum wells Institute of Applied Physics and Laboratory for Emerging

Nanometrology, Technische Universität Braunschweig,

38106 Braunschweig, Germany

Physical Review B

https://doi.org/10.1103/PhysRevB.99.205308

The radiative rate of GaInN/GaN quantum well

structures on nonpolar substrates is investigated for

different quantum well widths, showing a

https://doi.org/10.1039/C9NR02823D

https://doi.org/10.7567/1347-4065/ab1252



significant decrease of the radiative emission

towards larger well widths. This effect can be

explained by the strict selection rules that apply for

radiative transitions in nonpolar structures without

any polarization fields in the direction of

quantization. The selection rule Δn=0 reduces the

number of possible radiative transitions that involve

higher quantized hole states. These states will get

occupied towards room temperature for wider

quantum wells due to the decrease in quantization

energies. Since the effective masses are strongly

different in the conduction and valence bands, the

thermal population of higher states is imbalanced

between electrons and holes. Applying a simple

model in a nondegenerate limit, we can well

describe the width dependence of the

experimentally determined radiative rates. At room

temperature, the decrease amounts to a factor of

2–4 for nonpolar quantum wells of 8nm thickness.

Controlled crystal orientations of semipolar AlN

grown on an m-plane sapphire by MOCVD RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan


https://doi.org/10.7567/1347-4065/ab0f1c

The way to control AlN orientations on an m-plane

sapphire in metal-organic chemical vapor

deposition has not been clarified. We investigated

the effect of the nitridation process on the crystal

orientation of semipolar AlN on an m-plane

sapphire. In terms of substrate heating, (10-1-3) AlN

was obtained under H2 without NH3, whereas (11–

22) AlN was obtained by heating with H2 and NH3.

Temperature-dependent nitridation demonstrated

that the AlN orientation changed from (10-1-3) to

(11–22) at the nitridation temperature of 500 °C,

which can be explained by the formation of r-plane

nanofacets on m-plane sapphire under significant

nitridation at a high temperature. At a nitridation

temperature of 1100 °C, a small amount of NH3 led

to the formation of (11–22) AlN, indicating that care

must be taken to keep the reactor conditions for

producing desired AlN orientations with

reproducibility.

Valence band structure and effective masses of

GaN(10¯10) Institut für Festkörperphysik, Technische Universität

Berlin, 10623 Berlin, Germany

Peter Grünberg Institut, Forschungszentrum Jülich

GmbH, 52425 Jülich, Germany

Physical Review B


The electronic structure of the clean and

stoichiometric GaN(10¯10) cleavage surface is

investigated in a comprehensive angle-resolved

photoelectron spectroscopy study. A clear

distinction between surface and bulk related

features allows us to measure the dispersions of the

occupied surface state band from the N dangling

bonds as well as of the uppermost bulk valence

bands and to extract the effective hole masses

directly with high precision. This is performed along

various directions in k∥ space providing a detailed

picture of the electronic band dispersion. The

obtained results show three separated bulk bands

without indications of a crossing of these bands as

commonly predicted in theoretical works.

Moreover, from the observed Fermi-level pinning

we determine the position of the minimum of the

empty Ga-derived surface state band, which is

found deep within the fundamental band gap at

∼2.3 eV above the valence band maximum.

MATERIAL / CHARACTERIZATION /

EQUIPMENT / NUMERICAL SIMULATION Information selected by

Yvon Cordier (CRHEA-CNRS)

Highly efficient p-type doping of GaN under

nitrogen-rich and low-temperature conditions by

plasma-assisted molecular beam epitaxy National Research Council, Ottawa, Ontario K1A 0R6,

Canada

AIP Advances

https://doi.org/10.1063/1.5089658

Highly efficient and reproducible p-type doping of

GaN under nitrogen-rich and low-growth-

temperature conditions was demonstrated with the

plasma-assisted molecular beam epitaxy technique.

https://doi.org/10.7567/1347-4065/ab0f1c


https://doi.org/10.1063/1.5089658


The low-temperature range is approximately below

650 °C and refers to growth temperatures at which

the thermal desorption of any excess Ga is

negligibly slow. The Mg and hole concentrations

obtained with the N-rich condition were more than

one order of magnitude higher than those obtained

with the Ga-rich condition while keeping all other

conditions identical. The Mg doping under such N-

rich conditions was also found to show Mg-

mediated suppression of background impurities,

good epitaxy quality on GaN templates, and

relatively low surface roughness. Over the

investigated growth temperature range from 580 °C

to 650 °C, the Mg incorporation efficiency under the

N-rich condition was found to be close to unity

(70%-80%) and independent of the growth

temperature. High hole concentrations of up to

2×1019 cm-3 and activation efficiencies of up to

16.6% were obtained. The result rules out the Mg

surface sticking probability as the limiting

mechanism for Mg incorporation in this

temperature range, as it would be temperature

dependent. Instead, the Mg incorporation rate was

more likely governed by the availability of

substitutional sites for Mg on the surface, which

should be abundant under the N-rich growth

conditions. Excellent diode characteristics and

electroluminescence results were observed when

this p-type doping method was employed in the

growth of full device structures.

Interface-phonon–electron interaction potentials

and dispersion relations in III-nitride-based

structures Electrical and Computer Engineering, University of Illinois

at Chicago, Chicago, Illinois 60607, USA

Department of Physics, University of Illinois at Chicago,

Chicago, Illinois 60607, USA

Department of Bioengineering, University of Illinois at

Chicago, Chicago, Illinois 60607, USA

U.S. Army Research Laboratory, 2800 Powder Mill Road,

Adelphi, Maryland 20783, USA


https://doi.org/10.1063/1.5086306

In dimensionally confined multilayer

heterostructures, phonons that are joint modes of

the materials composed of these heterostructures

are known to exist over specific frequency ranges.

These modes, known as interface phonons, can

exhibit phonon-electron interactions that are

enhanced as the thicknesses of the layers of the

heterostructure are reduced in size to about 10 nm

or less. These modes have been shown to be

important in phonon engineering and have been

applied in optoelectronic and electronic devices,

primarily for semiconductor heterostructures with

underlying cubic lattices, with few studies existing

for heterostructures based on wurtzite III-nitride.

Motivated by applications of interface modes in

ternary-based nitride structures, such as heat

transport, this paper presents generalized

expressions for the phonon-electron Fröhlich

interactions as well as the dispersion relations for

these joint modes for the technologically important

case of III-nitride materials. Frequency conditions

are found to restrict the existence of interface

modes as illustrated through several structures.

Single- and double-resonant enhancement of

second-harmonic generation in asymmetric

AlGaN/GaN/AlGaN quantum well heterostructures Laboratoire de Micro-Optoélectronique et

Nanostructures, Université de Monastir, Faculté des

Sciences de Monastir, Avenue de l’Environnement, 5019

Monastir, Tunisia


https://doi.org/10.1063/1.5079660

The second-harmonic generation susceptibility is

theoretically investigated based on the compact

density-matrix formalism in two- and three-level

AlGaN/GaN systems. The electronic states and their

related wave functions were calculated by solving

self-consistently the Schrödinger–Poisson equations

within the effective mass and Hartree

approximations. The presence of spontaneous and

piezoelectric polarizations is taken into account in

the modeling part. It was revealed from the

relevant results that (i) the second-order

susceptibility shows a multiple peak structure due

to intersubband and their corresponding virtual

transitions, (ii) the use of a back doping as well as

the optimization of the layer widths in delta-doped

AlGaN/GaN asymmetric quantum wells improved

considerably the second-harmonic susceptibility,

https://doi.org/10.1063/1.5086306

https://doi.org/10.1063/1.5079660


and (iii) the three-level AlGaN/GaN system is the

most efficient structure, which generates the

second-harmonic with a significant intensity up to

4.36 × 10−5 mV−1. Numerical results of the present

work could lay the basis for research in AlGaN-

related optoelectronic device applications.

Impact of Cone‐Shape‐Patterned Sapphire

Substrate and Temperature on the Epitaxial

Growth of p‐GaN via MOCVD Key Laboratory of Semiconductor Materials Science,

Institute of Semiconductors, Chinese Academy of

Sciences, P. O. Box 912, Beijing 100083, People’s

Republic of China

Beijing Key Laboratory of Low Dimensional

Semiconductor Materials and Devices, Institute of

Semiconductors, Chinese Academy of Sciences, P. O. Box

912, Beijing 100083, People’s Republic of China

Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,

Beijing 101408, People’s Republic of China



In this paper, the authors report both the effects of

the cone‐shape‐patterned sapphire substrate

(CSPSS) and the growth temperature on surface

morphology and crystalline quality of the p‐GaN

layers, grown via metal‐organic chemical vapor

deposition (MOCVD). Low‐temperature GaN buffer

and high‐temperature undoped GaN (u‐GaN)

coalescence layers are grown between p‐GaN

epitaxial film and substrate for all the samples. The

time evolution of surface morphology of those films

is monitored by scanning electron microscope

(SEM) in order to investigate the growth

mechanism of films on CSPSS. The compressive

stresses in the p‐GaN films is also discussed. From

atomic force microscopy (AFM) and X‐ray

diffraction (XRD) results, it is observed that, using

CSPSS at a lower temperature (1030 °C) significantly

reduces the surface roughness and enhances the

crystallinity of p‐GaN film compared to growth at

1060 °C on conventional sapphire substrate.

Furthermore, the low resistivity level of 0.05 Ω cm

and high hole carrier concentration of

1.57 × 1019 cm−3 in the p‐GaN have been achieved

by using CSPSS at lower temperature.

Time-resolved photoluminescence from n-doped

GaN/Al0.18Ga0.82N short-period superlattices

probes carrier kinetics and long-term structural

stability Max-Born-Institut für Nichtlineare Optik und

Kurzzeitspektroskopie, Max-Born-Str. 2A, 12489 Berlin,

Germany

Ferdinand-Braun-Institut, Leibniz-Institut für

Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489

Berlin, Germany


https://doi.org/10.1063/1.5078668

Heavily n-doped GaN/Al0.18Ga0.82N short-period

superlattices with and without SiN protection layers

are studied in spectrally and temporally resolved

photoluminescence (PL) experiments. The room-

temperature PL from a protected sample displays a

nonexponential decay with an initial decay time of

150 ps for low excitation levels and an exponential

decay with a time constant of ∼300 ps for higher

excitation. The PL decays are governed by

nonradiative carrier relaxation into deep defect

states which are partially saturated at high

excitation densities. PL measurements at low

sample temperature reveal a marked influence of

carrier cooling on the PL kinetics in a time range up

to 50 ps and a significant radiative decay

component. SiN coatings are shown to provide

long-term stabilization of surface morphology while

increasing nonradiative carrier relaxation rates.

Investigation of GaN with Low Threading

Dislocation Density Grown on Graphene/Sputtered

AlN Composite Substrate State Key Discipline Laboratory of Wide Band Gap

Semiconductor, Technology School of Microelectronics,

Xidian University, No.2 South TaiBai Road, Xi’an 710071,

China

School of Aerospace Science and Technology, Xidian

University, No.2 South TaiBai Road, Xi’an 710071, China

physica status solidi rrl

https://doi.org/10.1002/pssr.201900167

High‐quality GaN film is grown on graphene with

the underneath sputtered AlN modified layer using

metal organic chemical vapor deposition. Due to

the modulation effect of sputtered AlN on the


https://doi.org/10.1063/1.5078668

https://doi.org/10.1002/pssr.201900167


surface potential and the chemical reactivity of

graphene, the nucleation probability of GaN is

significantly improved. The GaN epitaxial layer

shows excellent crystal quality and surface

morphology, and has very low threading dislocation

density of 1.78 × 108 cm−2. Furthermore, the

mechanism of threading dislocation suppression is

revealed according to the transmission electron

microscope results. The improved nucleation

probability and enhanced lateral growth mode lead

to the formation of short‐range stacking faults in

c‐plane GaN, which block the propagation of

threading dislocations along the growth direction.

Moreover, the formation and evolution mechanism

of the short‐range stacking faults are discussed. The

results in this work not only offer a promising

approach to propel the widespread application of

GaN on graphene, but also provide a new idea for

the regulation and suppression of defects in the

growth of nitride semiconductors.

Monolayer GaN functionalized with alkali metal

and alkaline earth metal atoms: A first-principles

study Department of Electrical and Electronic Engineering, Lee

Kong Chian Faculty of Engineering and Science, Universiti

Tunku Abdul Rahman, Kajang, Selangor, 43000, Malaysia

School of Physics, Universiti Sains Malaysia, USM,

Penang, 11800, Malaysia

Faculty of Engineering and Technology, Multimedia

University, Jalan Ayer Keroh Lama, Melaka, 75450,

Malaysia

Center for Foundation Studies, International University

of Malaya-Wales, Kuala Lumpur, 50480, Malaysia

Faculty of Engineering, Multimedia University, Persiaran

Multimedia, Cyberjaya, Selangor, 63100, Malaysia



Based on first-principles calculations, we have

carried out a systematic study on the geometric,

electronic and magnetic properties of free-standing

monolayer GaN (ML GaN) functionalized with

Lithium (Li), Sodium (Na), Beryllium (Be) or Calcium

(Ca) atoms. We consider three different levels of

concentrations i.e. , and . Within the tested,

metallization of ML GaN only occurs with the

adsorption of Li or Na atoms. The adsorption of Be

or Ca atoms preserves the semiconducting

characteristics of ML GaN. The ML GaN remains

non-magnetic with the adsorption of Be or Ca atom.

In contrast, the total magnetization of the Li-

adsorbed ML GaN decreases as Li atoms

concentration increases. For the case of Na

adsorption, the ML GaN exhibits ferromagnetism

only at . In addition, we found the work function of

the functionalized ML GaN can be controlled by

varying the concentrations of the adatoms. Our

findings here suggest that by selective adsorption of

Group I and Group II element, ML GaN is a

promising material for the development of

spintronic and field emission devices.

GaN in different dimensionalities: Properties,

synthesis, and applications College of Chemistry and Molecular Sciences, Wuhan

University, Wuhan 430072, China

The Institute for Advanced Studies (IAS), Wuhan

University, Wuhan 430072, China

Suzhou Institute of Nano-Tech and Nano-Bionics

(SINANO), Chinese Academy of Sciences, Suzhou 215123,

China

Materials Science and Engineering: R: Reports

https://doi.org/10.1016/j.mser.2019.04.001

Wurtzite GaN materials underpin many aspects of

optoelectronic applications due to the special

tetrahedral-coordinated structure. Compared with

three dimensional (3D) GaN, low dimensional GaN

provides structural and electronic changes, such as

different geometrical configuration, surface trapped

states and quantum confinement effect, which

impose dramatic effects on the properties and even

the ultimate applications. To construct desirable

devices and expand the scope of applications for

GaN, it necessitates an in-depth understanding of

the dimensionality-dependent property. In this

review, we firstly review the structure and

properties of GaN in different dimensionalities.

Successively, strategies for realizing the synthesis of

GaN with various dimensionalities are generalized.

Afterwards, we examine how their structure and

properties are utilized in the significant applications

involving microelectronic devices and energy

conversion fields. Finally, we conclude by outlining

a few research directions of GaN semiconductors


https://doi.org/10.1016/j.mser.2019.04.001


that might be worthwhile for exploration in the

future.

Determination of energy thresholds of electron

excitations at semiconductor/insulator interfaces

using trap-related displacement currents Semiconductor Physics Laboratory, University of Leuven,

3001 Leuven, Belgium

PGI 9-IT, Forschungszentrum Jülich GmbH, 52425 Jülich,

Germany



Spectral measurements of illumination-induced

displacement currents related to trapping of charge

carriers optically excited in semiconductor

electrodes are shown to deliver information

regarding energy onsets of electron transitions at

the interface. Presented examples include

determination of the conduction band offset at the

GaN/Al2O3 interface and determination of charge

carrier excitation spectra of two-dimensional (2D)

semiconductors MoS2 and WS2 at the interface

with insulating SiO2.

Thermodynamic modeling of elastic mismatch

strain energy on epitaxial growth of GaInN thin

films Beijing Key Laboratory of Construction Tailorable

Advanced Functional Materials and Green Applications,

School of Materials Science and Engineering, Beijing

Institute of Technology, Beijing, 100081, PR China

Dept. of Chemical, Paper and Biomedical Engineering,

Miami University, Oxford, OH 45056, United States

Computer Network Information Center, Chinese

Academy of Sciences, Beijing, 100190, PR China

Journal of Alloys and Compounds

https://doi.org/10.1016/j.jallcom.2019.05.225

The effect of mismatch elastic strain energy

between GaInN epitaxial film and GaN (0001)

substrate is investigated by classical

thermodynamics combining with classical elastic

mechanics and first-principles calculations. The

mismatch elastic strain energies in different indium

content are calculated by classical mechanics with

stiffness coefficients determined by the first-

principles calculations. A negative excess term is

discovered in the mismatch strain energy of GaInN

epitaxial films. The negative excess term largely

counteracts the positive mixing enthalpy of GaInN

solution compound, suppressing the large

miscibility gap of GaInN alloy. The calculations well

explain the successful growth of GaInN epitaxial

films with high indium content. This work provides

an easy and logical approach to evaluate the

thermodynamics of lattice mismatch in various

material systems, such as heteroepitaxial growth,

second-phase precipitation, etc.

Growth and thermal annealing for acceptor

activation of p-type (Al)GaN epitaxial structures:

Technological challenges and risks Łukasiewicz Research Network - Institute of Electronic

Materials Technology, Wólczyńska 133, 01-919 Warsaw,

Poland



III-nitride materials, such as ternary alloys of gallium

nitride (GaN) and aluminum nitride (AlN), are the

prominent semiconductor systems in research and

industry due to their importance for optoelectronic

applications using ultraviolet (UV) spectral range.

Although significant efforts have been made over

the last two decades, the main drawback of

epitaxial structures hindering their full potential in

devices is still associated with obtaining reasonably

good p-doping control. Here, an effect of acceptor

activation by post-growth treatments, that is

conventional and rapid thermal annealing, was

studied, revealing that while selecting inappropriate

conditions p-type AlGaN structures with

microstructural degradation, surface precipitation,

Mg out-diffusion and poor electrical properties are

achieved. The observed planar segregation in a

form of pyramidal domains (Mg-rich features),

associated with Mg overdose and its limited

solubility in AlGaN (~5 × 1019 cm−3) results in a

decrease of the hole concentration. However, rapid

thermal annealing in oxidizing and then reducing

atmospheres leads to controlled oxygen co-doping

of a p-type layer, and at the same time acceptor

activation is enhanced and the carrier

concentration is increased, >1018 cm−3. Therefore,

rapid thermal annealing of Mg-doped AlGaN


https://doi.org/10.1016/j.jallcom.2019.05.225



structures, in particular using oxygen atmosphere,

is advantageous to obtain relatively high carrier

concentration and p-type conduction.

GaN crystals growth in the Na-Li-Ca flux by liquid

phase epitaxy (LPE) technique Electronic Materials Research Laboratory, Key Laboratory

of the Ministry of Education & International Center for

Dielectric Research, School of Electronic and Information

Engineering, Xi’an Jiaotong University, Xi’an 710049,

China

Journal of Crystal Growth


10 × 10 mm2 area GaN crystals were successfully

grown on HVPE-GaN seed by LPE technique in Na-

Li-Ca flux. Many growth hillocks with hexagonal

shape were formed on the surface of crystal when

the growth time was 150 h. Due to the lateral

growth, the smooth Ga-face could be obtained after

growth 300 h. The dislocation density could be

decrease from 107 cm−2 to 103 cm−2 with

increasing GaN crystal growth thickness. The

reduction mechanism of dislocation was discussed.

The PL spectra showed that the relative intensity of

the yellow band luminescence peak of GaN crystals

was obviously reduced comparing with HVPE-GaN

seed, which indicated that the impurity defects in

the crystal could be effectively suppressed.

Detailed surface analysis of V‐defects in GaN films

on patterned silicon(111) substrates by metal–

organic chemical vapour deposition National Institute of LED on Silicon Substrate, Nanchang

University, Nanchang, Jiangxi 330096, People’s Republic

of China

Journal of Applied Crystallography

https://doi.org/10.1107/S1600576719005521

The growth mechanism of V‐defects in GaN films

was investigated. It was observed that the crystal

faces of both the sidewall of a V‐defect and the

sidewall of the GaN film boundary belong to the

same plane family of \{ {{{10\bar 11}}} \}, which

suggests that the formation of the V‐defect is a

direct consequence of spontaneous growth like that

of the boundary facet. However, the growth rate of

the V‐defect sidewall is much faster than that of the

boundary facet when the V‐defect is filling up,

implying that lateral growth of \{ {{{10\bar 11}}} \}

planes is not the direct cause of the change in size

of V‐defects. Since V‐defects originate from

dislocations, an idea was proposed to correlate the

growth of V‐defects with the presence of

dislocations. Specifically, the change in size of the

V‐defect is determined by the growth rate around

dislocations and the growth rate around

dislocations is determined by the growth

conditions.

The new nitrides: layered, ferroelectric, magnetic,

metallic and superconducting nitrides to boost the

GaN photonics and electronics eco-system Electrical and Computer Engineering, Cornell University,

14853, Ithaca, New York, United States of America

Materials Science and Engineering, Cornell University,

14853, Ithaca, New York, United States of America

Applied Physics, Cornell University, 14853, Ithaca, New

York, United States of America


https://doi.org/10.7567/1347-4065/ab147b

The nitride semiconductor materials GaN, AlN, and

InN, and their alloys and heterostructures have

been investigated extensively in the last 3 decades,

leading to several technologically successful

photonic and electronic devices. Just over the past

few years, a number of "new" nitride materials

have emerged with exciting photonic, electronic,

and magnetic properties. Some examples are 2D

and layered hBN and the III–V diamond analog cBN,

the transition metal nitrides ScN, YN, and their

alloys (e.g. ferroelectric ScAlN), piezomagnetic

GaMnN, ferrimagnetic Mn4N, and epitaxial

superconductor/semiconductor NbN/GaN

heterojunctions. This article reviews the fascinating

and emerging physics and science of these new

nitride materials. It also discusses their potential

applications in future generations of devices that

take advantage of the photonic and electronic

devices eco-system based on transistors, light-

emitting diodes, and lasers that have already been

created by nitride semiconductors.


https://doi.org/10.1107/S1600576719005521

https://doi.org/10.7567/1347-4065/ab147b


Enhanced lateral growth of AlN epitaxial layer on

sapphire by introducing periodically pulsed-TMGa

flows State Key Laboratory of Optoelectronic Materials and

Technologies, School of Electronics and Information

Technology, Sun Yat-sen University, Guangzhou, 510275,

PR China



Crystal quality improvements of AlN epilayers

grown on sapphire substrates has been achieved by

using periodically pulsed-trimethylgallium (TMGa)

flows (PTFs) in the initial growth stage of high-

temperature AlN. The 400-nm-thick AlN layer

deposited with this method demonstrated

atomically flat surface, and the line widths of x-ray

rocking curves were 40 and 245 arcsec for (002) and

(105) reflections, respectively. GaN mole fraction

was measured to be less than 0.6% in the AlN layer,

indicating a surfactant effect of the PTFs. A

combination of experimental characterizations and

density functional theory calculations unveils that

the improvements are ascribed to the supplement

of Ga atoms and the enhanced surface migration of

Al adatoms by using the PTFs which promotes the

transition of growth mode from three-dimension to

two-dimension one.

Impact of metalorganic vapor phase epitaxy

growth conditions on compressive strain

relaxation in polar III-nitride heterostructures STR Group—Soft-Impact, Ltd., 64 Bolshoi Sampsonievskii

Ave., Bld. 'E', 194044 St. Petersburg, Russia


https://doi.org/10.7567/1347-4065/ab06b7

A novel approach to estimating the critical

thicknesses (CTs) of compressively strained III-

nitride layers is suggested, based on a quasi-

thermodynamic growth model and accounted for

the effect of material decomposition during

dislocation half-loop formation on the CT value. The

approach provides good quantitative agreement

with available data on CTs of MOVPE-grown

InGaN/GaN and AlGaN/AlN epilayers. The

extremely large CTs observed for high Al-content

AlGaN alloys grown on bulk AlN substrates may be

attributed, in particular, to the dominant AlGaN

decomposition mechanism, producing group-III

metallic liquid and gaseous nitrogen. The suggested

approach may also be helpful for analysis of

threading dislocation inclination in compressively

strained layers and applicable to studying point

defect formation in semiconductors and its

dependence on growth conditions.

AlGaN/GaN high electron mobility transistor

heterostructures grown by ammonia and

combined plasma-assisted ammonia molecular

beam epitaxy King Abdulaziz City for Science and Technology, National

Nanotechnology Center, PO Box 6086, 11442 Riyadh,

Saudi Arabia

Institute of Physics of NAS of Belarus, 68 Nezalezhnasci

Ave, 220072 Minsk, Belarus

Tyndall National Institute, University College Cork, Lee

Maltings, Dyke Parade, T12R5CP Cork, Ireland

SemiTEq JSC, 27 Engels Ave, 194156 Saint-Petersburg,

Russia


https://doi.org/10.7567/1347-4065/ab06b4

The structural properties and surface morphology

of AlN epitaxial layers grown by ammonia (NH3)

and plasma-assisted (PA) molecular beam epitaxy

(MBE) at different growth conditions on (0001)

sapphire were investigated. The lowest RMS

roughness of ~0.7 nm was achieved for the sample

grown by NH3 MBE at a substrate temperature of

1085 °C and NH3 flow of 100 standard cm3 min−1.

Atomic force microscopy measurements

demonstrated a terrace-monolayer step-like surface

morphology. Furthermore, the optimal substrate

temperature for growth of GaN and AlGaN layers

was determined from analysis of the GaN thermal

decomposition rate. Using the optimized growth

conditions, high electron mobility transistor

heterostructures were grown by NH3 MBE on

different types of AlN nucleation layer deposited by

NH3 MBE or PA MBE. The grown heterostructures

demonstrated comparable two-dimensional

electron gas (2DEG) properties. The maximum 2DEG

mobility of ~2000 cm2 V–1 s–1) at a 2DEG density

of ~1.17 × 1013 cm−2 was achieved for the


https://doi.org/10.7567/1347-4065/ab06b7

https://doi.org/10.7567/1347-4065/ab06b4


heterostructure with a PA MBE-grown AlN

nucleation layer. The obtained results demonstrate

the possibility of successful combination of

different epitaxial approaches within a single

growth process, which will contribute to the

development of a new type of hybrid epitaxy that

exploits the advantages of several technologies.

A 300 nm thick epitaxial AlInN film with a highly

flat surface grown almost perfectly lattice-

matched to c-plane free-standing GaN substrate Research Center for Nano Devices and Advanced

Materials, Nagoya Institute of Technology, Nagoya 466-

8555, Japan

Innovation Center for Multi-Business of Nitride

Semiconductors, Nagoya Institute of Technology, Nagoya

466-8555, Japan

Faculty of Science and Technology, Meijo University,

Nagoya 468-8502, Japan


https://doi.org/10.7567/1347-4065/ab040c

Single-layer AlInN films with a film thickness of

approximately 300 nm were grown on a c-plane

free-standing (FS) GaN substrate by metalorganic

chemical vapor deposition. The result showed that

a highly flat-surface AlInN film with a small root-

mean-square surface roughness of less than 0.5 nm

was realized by adjusting its alloy composition to an

almost perfectly lattice-matched to FS-GaN. As for

the highly flat-surface AlInN film, the optical

constants were evaluated in whole visible

wavelength by spectroscopic ellipsometry. Then, its

energy bandgap energy was determined to be 3.92

eV.

Plasma assisted-MBE of GaN and AlN on graphene

buffer layers National Research Nuclear University MEPhI, Moscow,

115409, Russia

Belarusian State University of Informatics and

Radioelectronics, Minsk, 220013, Belarus


https://doi.org/10.7567/1347-4065/ab124b

The possibility of using chemical vapor deposition

(CVD) graphene as a 2D buffer layer for epitaxial

growth of III-nitrides by plasma assisted-MBE on

amorphous substrates (SiO2 prepared by thermal

oxidation of Si wafer) was investigated. The

comparative study of graphene-coated parts of the

wafers and the parts without graphene was carried

out by scanning electron microscopy and X-ray

diffractometry. It was shown that epitaxial GaN and

AlN films with close to 2D surface morphology can

be obtained by plasma assisted-MBE on amorphous

SiO2 substrates with a multilayer graphene buffer

using the HT AlN nucleation layer.

The role of Si in GaN/AlN/Si(111) plasma assisted

molecular beam epitaxy: polarity and inversion Physical Measurement Laboratory, National Institute of

Standards and Technology, Boulder, CO 80305, United

States of America


https://doi.org/10.7567/1347-4065/ab1124

The microstructure, polarity and Si distribution in

AlN/GaN layers grown by plasma assisted molecular

beam epitaxy on Si(111) was assessed by scanning

transmission electron microscopy. Samples grown

under both metal- and nitrogen-rich conditions

contained defects at the AlN/Si interface which

suggest formation of an Al-Si eutectic. Correlated

with this, interfacial segregation of Si was found in

the samples. It is proposed that Si is dissolved in a

eutectic layer floating on the AlN surface under

metal-rich conditions. This Si is then incorporated

into the film if the growth becomes nitrogen-rich,

either intentionally or due to plasma source

transients. These Si-rich layers appear to induce

inversion of the nitride from nitrogen- to metal-

polarity, and uncontrolled variations in the Si

concentration cause occasional nonuniformity in

the resulting inversion.

Impact of low-temperature annealing on defect

levels generated by Mg-ion-implanted GaN Research Center for Integrated Quantum Electronics,

Hokkaido University, Sapporo 060-0813, Japan


https://doi.org/10.7567/1347-4065/ab09d5

The impact of low-temperature annealing on Mg-

ion-implanted GaN with a low dosage (1.5 × 1011

https://doi.org/10.7567/1347-4065/ab040c

https://doi.org/10.7567/1347-4065/ab124b

https://doi.org/10.7567/1347-4065/ab1124

https://doi.org/10.7567/1347-4065/ab09d5


cm−2) has been investigated using MOS diodes.

Low-temperature annealing was carried out for Mg-

ion-implanted GaN in the temperature range from

400 °C to 700 °C before forming the

insulator/semiconductor interface of the tested

MOS diodes. Upon annealing, the hysteresis and

the slope of the capacitance–voltage (C–V) curves,

which were affected by deep levels in the GaN bulk,

were changed with the annealing temperature. In

particular, the shape of C–V curve was changed by

annealing at a temperature as low as 500 °C. The C–

V curves were found to be reproducible by a

simulation in which the dominant deep levels were

assumed to be located at 0.1 and 0.7 eV below the

conduction band edge. Considering the low

recovery temperature and low dosage, the

possibility of the existence of simple defects after

implantation is discussed.

Oxygen and silicon point defects in Al0.65Ga0.35N Department of Materials Science and Engineering, North

Carolina State University, Raleigh, North Carolina 27695,

USA

Physical Review Materials

https://doi.org/10.1103/PhysRevMaterials.3.054604

The formation energies of oxygen and silicon

impurities have been examined explicitly in

Al0.65Ga0.35N using hybrid exchange-correlation

density-functional theory simulations. Both

impurities were initialized in on-site substitutional

and off-site DX configurations in a range of charge

states. The O+1N donor was found to always relax

into an on-site configuration, and its formation

energy is relatively independent of local chemistry

(the configuration of Al and Ga atoms surrounding

the defect). By contrast, the O−1N acceptor almost

always relaxes into a DX configuration, with a

formation energy that is strongly dependent on

local chemistry. The differences in formation energy

of distinct O−1N defect configurations are

understood through the interplay of two qualitative

trends in the types of nearest-neighbor bonds (O-Al

or O-Ga), as well as the subtler influence of the

lengths of the O-Al bonds. Knowledge of O−1N

formation energies as well as the relative

frequencies of sites with different local chemistry

allows one to compute the relative site occupancies

of O−1N. Because the thermodynamic transition

levels associated with different defect

configurations are unique, the ON DX transition is

associated with multiple defect levels. SiIII, where III

represents the group III cation of Al or Ga, provides

an interesting counterexample. Si+1III is predicted

to be the dominant charge state across the entire

band gap of Al0.65Ga0.35N, and little dependence

of the formation energy on the composition of

nearby cation sites was found. This is explained by

the fact that the first-nearest neighbors are all of

the same species (N), so the local environment is

similar to a bulk III nitride, in which on-site Si+1III is

stable across the same Fermi level range (i.e., below

the band gap of Al0.65Ga0.35N). Thus, the trends in

the energetics of ON and SiIII in Al0.65Ga0.35N are

both determined by the chemistry of the four

nearest-neighbor sites surrounding the defect site.

Analysis of strain and dislocation evolution during

MOCVD growth of an AlGaN/GaN power high-

electron-mobility transistor structure STR Group—Soft-Impact, Ltd., 64 Bolshoi Sampsonievskii

pr., Build. "E" 194044, St. Petersburg, Russia

ON Semiconductor Czech Republic, s.r.o., 1. maje 2230

Roznov pod Radhostem, 756 61 Czechia


https://doi.org/10.7567/1347-4065/ab138e

We present the results of a comprehensive analysis

of GaN-on-Si based HEMT epi-wafers grown by

metal-organic chemical vapor deposition (MOCVD)

in a production-scale reactor. An AlGaN/AlN

superlattice was used as the buffer layer. Detailed

characterization was combined with process

modeling by STREEM-AlGaN software. Comparative

analysis of modeling results, characterization data,

and in situ curvature measurements allows the

study of the evolution of structural properties of

the epi-wafer during growth. The initial

compressive mean stress in the superlattice

gradually decreases during starting period of the

growth and then becomes almost constant. The

filtering of the dislocations is more effective in the

bottom part of the SL, as both experiment and

modeling demonstrate large inclination of

dislocations in AlGaN layers of the superlattice,

while the predicted dislocation density decreases

https://doi.org/10.1103/PhysRevMaterials.3.054604

https://doi.org/10.7567/1347-4065/ab138e


due to annihilation. Proposed buffer layer and

growth recipe resulted in final reduction of the

dislocation density to ~2 centerdot 108 cm−2 with

good structural uniformity over 6'' wafers and a

residual bow below 50 μm.


PRESS RELEASE Technical and economic information selected by Knowmade

ELECTRONICS

NXP unveils RF power portfolio for 5G cellular infrastructure SemiconductorToday

NXP Semiconductors N.V. of Eindhoven, The Netherlands has unveiled what it claims is one of the industry’s

most integrated portfolios of RF solutions for 5G cellular infrastructure, industrial and commercial markets,

exceeding existing 5G RF power amplification demands for base stations - from MIMO to massive MIMO-based

active antenna systems for cellular and millimeter-wave (mmWave) spectrum bands.

The firm says that its radio power solutions also simplify mMIMO deployments by enabling smaller, lighter

active antenna systems, and its RF power multi-chip modules (MCMs) offer high levels of integration and

performance. With solutions from sub-6GHz to 40GHz and from milliwatts to kilowatts, NXP aims to further

simplify 5G infrastructure to allow partners to rapidly develop systems and join the 5G ecosystem.

“With the potential to transform entire industries and economies, 5G will be fully realized over time and NXP is

uniquely positioned to facilitate its global adoption by offering one of the industry’s most comprehensive

cellular infrastructure portfolio focused on driving the 5G-connected world,” believes Paul Hart, senior VP &

general manager of NXP’s Radio Power Solutions. “NXP is ahead of the demand curve as the world’s top supplier

of massive MIMO solutions enabling carriers to provide more bandwidth to customers,” he adds.

NXP says it is enabling many of the world’s first RF deployments in 5G for both sub-6GHz mMIMO and the first

millimeter-wave networks. The firm adds that at the core of this is its trifecta of radio power solutions:

• Smart antenna solutions, including highly integrated analog beam-forming products (operating at

frequencies of 24-40GHz) that leverage NXP’s silicon germanium (SiGe) technology for 5G millimeter-

wave infrastructure. The solutions enable customers to build the 5G mmWave phased-array antenna

systems of the future and serve consumers with substantial bandwidths in both fixed wireless access

(FWA) and radio access networks (RAN) applications.

• Integrated, high-efficiency power solutions, with 5G mMIMO and IC products for base stations across all

sub-6GHz cellular bands.

• Discrete high-power RF transistors for 4G and 5G MIMO-based cellular base stations, plus a full suite of

gallium nitride (GaN) RF and LDMOS RF power solutions for industrial, scientific & medical (ISM),

broadcast, RF energy, mobile radio and aerospace & defense applications.

Claiming to be the only company delivering RF and transceiver solutions across the complete range of 5G

network deployments from sub-6GHz to mmWave, NXP has established hardware and software partnerships

with key multiple-system operators (MSOs) and original design manufacturers (ODMs) to quickly deliver systems

for 5G hyper-connectivity to the market.

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Qorvo GaN and GaAs amplifiers selected for Syrlinks’ telemetry, tracking and control modules in Airbus OneWeb LEO satellites SemiconductorToday

Qorvo Inc of Greensboro, NC, USA (which provides core technologies and RF solutions for mobile, infrastructure

and defense applications) says that its amplifiers are being used in the telemetry, tracking and control modules

developed by Syrlinks of Cesson-Sévigné, near Rennes, France, for low Earth orbit (LEO) satellites. The first six

satellites of the constellation, designed by Airbus OneWeb Satellites, were recently launched to provide internet

connectivity almost anywhere in the world. Qorvo says that the reliability and performance of its products

reduce stress on the satellite power systems and ensure signal integrity in both transmit and receive modes.

Syrlinks specializes in radio communication and geolocation subsystems for space, defense and safety

applications. Its NewSpace products meet the new requirements of the space industry. Syrlinks’ telemetry,

tracking and control modules enable remote sensing and monitoring of the Airbus OneWeb LEO satellites for

internet connectivity service.

Close collaboration and flexibility across both companies’ functional teams were key to the project. Syrlinks

integrated the Qorvo RF front-end components into the space-qualified module and provided product definition

and performance requirements for the Qorvo products. Qorvo provided product application, manufacturing and

test support.

The MMIC power amplifier selected is fabricated on Qorvo’s highly reliable and efficient QGaN15 0.15µm

gallium nitride (GaN) process technology, which supports high-frequency applications through 40GHz. The low-

noise amplifier (LNA) is fabricated on Qorvo’s QPHT09 90nm gallium arsenide (GaAs) pseudomorphic high-

electron-mobility transistor (pHEMT) process, which has what is claimed to be a best-in-class noise figure. Qorvo

has nearly 100 commercial products (die and package options) built on these processes.

“Syrlinks has been investing for three years in the NewSpace approach associated with the latest generation of

components,” says the firm’s CEO Guy Richard. “These efforts required stronger links with manufacturers of

high-performance and innovative components, such as Qorvo,” he adds.

“Qorvo’s commercially packaged products are proving their operational readiness to meet the harsh

environment of space,” says Roger Hall, general manager, Qorvo High Performance Solutions. “By combining

powerful process technology with advances in packaging, Qorvo is enabling high-power devices that also

achieve high reliability and are operationally rugged.”

NXP unveils first GaN-on-SiC transistor for 2.45GHz RF energy surpassing efficiency of most magnetrons SemiconductorToday

At the IEEE’s International Microwave Symposium (IMS 2019) in Boston, MA, USA (4–6 June), NXP

Semiconductors N.V. of Eindhoven, The Netherlands has unveiled what it claims is the first RF power transistor

designed for RF energy using gallium nitride on silicon carbide (GaN-on-SiC). Leveraging the high efficiency of

GaN, the MRF24G300HS exceeds the efficiency of most magnetrons at 2.45GHz, while the high thermal

conductivity of SiC helps to ensure continuous wave (CW) operation.

For more than 50 years, 2.45GHz magnetrons have been widely used in consumer and industrial applications

ranging from microwave ovens to high-power welding machines. Solid-state solutions appeared on the market

several years ago, bringing advanced control, reliability and ease of use. The capability to dynamically adjust the

power, frequency and phase helps to optimize the energy transmitted to the material or food being heated. The

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long lifetime of transistors at full rated performance reduces the need for replacements. However, until the

advent of GaN-on-SiC for RF energy, solid-state devices lacked the efficiency to meet the incumbent

magnetrons’ performance standards.

The MRF24G300HS is a 330W CW, 50V GaN-on-SiC transistor, demonstrating 73% drain efficiency at 2.45GHz,

which is five points higher than the latest LDMOS silicon technologies. The high power density of GaN enables

the device to reach high output power in a small footprint. GaN technology has an inherently high output

impedance that allows broadband matching compared with LDMOS. This reduces the design time and ensures

consistency on the manufacturing line, so no more hand tuning is needed. The simplified gate biasing of the

MRF24G300HS RF transistor removes another step of the otherwise complex power-up sequence typically seen

on GaN devices.

“The smart control, low maintenance and ease of use of solid-state open the door to new use cases, such as

smart cooking and industry 4.0 heating machines,” says Paul Hart, senior VP & general manager of NXP’s Radio

Power Solutions. “By breaking the efficiency barrier of vacuum tubes, we enable our customers to unlock

innovation without any compromise on performance.”

The MRF24G300HS RF transistor is sampling now and production is planned for third-quarter 2019. The 2400-

2500MHz reference circuit is available now, under order number MRF24G300HS-2450MHZ. As part of the NXP

Partner Program, Prescient Wireless Inc has designed a 2-up, 550W power amplifier pallet with 45dB of gain,

which will be shown at IMS.

EPC to provide eGaN power devices in wafer form for ease of power systems integration SemiconductorToday

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA – which makes enhancement-mode gallium

nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications – has

announced the availability of its enhancement-mode GaN devices in wafer form for ease of integration. The

firm’s eGaN FETs and ICs are traditionally sold as singulated chip-scale devices with solder bars or solder bumps.

Chip-scale packaging is a more efficient form of packaging that reduces the resistance, inductance, size, thermal

impedance and cost of power transistors. These attributes of eGaN devices enable unmatched in-circuit

performance at competitive prices, claims EPC.

Wafer-level offerings of these devices allows easier integration in customer power system sub-assemblies,

further reducing device interconnect inductances and the interstitial space needed on the printed circuit board

(PCB), says the firm, adding that this increases both efficiency and power density while reducing assembly costs.

“We have listened to our partners and are pleased to offer our industry-leading GaN products in wafer form that

can accommodate a variety of assembly techniques and applications,” says CEO & co-founder Alex Lidow.

EPC is offering eGaN power devices in wafer form either with or without solder bumps. Extra services such as

wafer thinning, metallization of the wafer backside and the application of backside coating tape are also

available.

Qorvo unveils 10W Ka-band GaN amplifier for radar and EW applications SemiconductorToday


and defense applications) has unveiled a monolithic microwave integrated circuit (MMIC) power amplifier that

delivers more than 10W of saturated power over the 32-38GHz band. The reliability and efficiency of the

http://www.semiconductor-today.com/news_items/2019/jun/epc-040619.shtml

http://www.semiconductor-today.com/news_items/2019/jun/qorvo2-040619.shtml


product – said to be the highest-performing MMIC on the market – enable performance objectives to be

achieved in critical defense applications while reducing costs, says the firm.

Fabricated on Qorvo’s gallium nitride on silicon carbide (GaN-on-SiC) technology, the 10W TGA2222 provides

16dB of large-signal gain, 25dB of small-signal gain and what is claimed to be industry-leading power-added

efficiency greater than 22%. It delivers this extended RF power in a smaller die, which reduces the size (to

3.43mm x 2.65mm x 0.05mm), weight and number of components to create a simple solution for radar and

electronic warfare (EW) applications.

“The increasing demand for higher data rates across all markets continues to drive the need for better-

performing RF solutions,” notes Roger Hall, general manager of Qorvo’s High Performance Solutions business.

“With the TGA2222 [available now to qualified customers], Qorvo is delivering a breakthrough MMIC with the

industry’s highest levels of power and bandwidth for Ka-band defense applications,” he adds.

Qorvo launches GaN PAs for mission-critical Ka-band satcom and X-band phased-array radar applications SemiconductorToday


and defense applications) has launched two new gallium nitride (GaN) power amplifier (PA) families for

domestic and international Ka-band satcom and X-band phased-array radar applications. The solutions, which

are claimed to deliver best-in-class power, linearity and efficiency in a smaller footprint, enable higher system

performance while reducing costs.

The QPA2212 for Ka-band applications has what is said to be the industry’s highest linearity for wideband multi-

carrier systems, delivering 20W of RF power operating over the 27-31GHz frequency band. There are also 14W

QPA2211D and 7W QPA2210D options. Delivering higher linear power in a single monolithic microwave

integrated circuit (MMIC) PA enables cost reduction and performance enhancing opportunities, the firm states.

The QPA2212D is available now in die form; packaged versions will be available in August.

Available now in both packaged and die versions, the QPA1022 for X-band phased arrays offers what is claimed

to be best-in-class power-added efficiency of 45% at 4W RF power in the 8.5-11GHz range - an increase of 8%

over previous products while providing 24dB large-signal gain. These capabilities translate into maximum power

with minimum heat, higher reliability and lower cost of ownership, says Qorvo, adding that designers can create

higher-density arrays and achieve greater range for the same power budget.

“These new amplifiers expand Qorvo’s already-large portfolio of differentiated GaN products for defense

applications,” says Dean White, director of defense and aerospace market strategy. “Their advanced capabilities

and packaging leverage our more than 30 years of expertise in designing and delivering RF solutions for this

market, and also offer viable options for commercial 28GHz 5G network design.”

WIN releases 0.15μm GaN process for high-power mmWave PA applications and 5G infrastructure SemiconductorToday

WIN Semiconductors Corp of Taoyuan City, Taiwan – the largest pure-play compound semiconductor wafer

foundry – has expanded its gallium nitride (GaN) portfolio with the commercial release of NP15-00, a 0.15μm-

gate technology that supports emerging mmWave PA applications including radar, satellite communications and

5G massive MIMO infrastructure. NP15-00 supports full MMICs enabling customers to design compact, linear or

saturated high-power amplifiers through 35GHz.

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NP15-00 GaN employs a source-coupled field plate for improved breakdown voltage, and operates at a drain

bias of 20V. This technology is fabricated on 100mm silicon carbide (SiC) substrates with through-wafer vias for

low-inductance grounding. In the 29GHz band, NP15-00 offers saturated output power of 3W/mm with 13dB

linear gain and greater than 50% efficiency without harmonic tuning.

“The release of NP15 expands WIN’s portfolio of mmWave compound semiconductor technologies for transmit

power amplifiers used in 5G mmWave radio access networks (RANs), satellite communications and radar

systems,” says senior VP David Danzilio. “For mmWave active arrays, the higher transmit power and efficiency

from NP15 affords designers greater flexibility to optimize antenna count, PA size and total array power,” he

adds. “Depending on where deployed, mmWave RAN infrastructure will leverage access points of various sizes,

shapes and power levels, and a broad trade-space is crucial to optimize the performance and economics of

mmWave active antenna systems.”

Wolfspeed presents new GaN-on-SiC and LDMOS components at IMS SemiconductorToday

In booth 842 at the IEEE’s International Microwave Symposium (IMS 2019) in Boston, MA, USA (4–6 June),

Wolfspeed of Durham, NC, USA — a Cree Company that makes silicon carbide (SiC) power products and gallium

nitride on silicon carbide (GaN-on-SiC) high-electron-mobility transistors (HEMTs) and monolithic microwave

integrated circuits (MMICs) — is exhibiting a broad assortment of GaN-on-SiC and laterally diffused metal-oxide-

semiconductor (LDMOS) devices, as well as introducing new products for aerospace/defense and

communications infrastructure applications.

Wolfspeed is also giving live demonstrations each day including:

• a broadband GaN monolithic microwave integrated circuit (MMIC) power amplifier (PA) for 32V counter

improvised explosive device (C-IED) applications;

• a mid-Ku-band GaN MMIC PA for satellite communications (SatCom) applications;

• a 63W average, 3.6-3.8GHz high-efficiency Doherty GaN transistor for cellular base-station transmitter

amplifiers;

• a broadband GaN MMIC power amplifier for 28V X-band radar applications including military, marine

and weather radars;

• a 120W multi-stage application fixture for S-band radar; and

• a troposcatter tactical radio reference design for SatCom and radio links.

Northrop Grumman’s GaN-based G/ATOR AESA radar system passes initial operational test & evaluation SemiconductorToday

Northrop Grumman Corp, in partnership with the United States Marine Corps, has passed an Initial Operational

Test and Evaluation (IOT&E) for the AN/TPS-80 Ground/Air Task-Oriented Radar (G/ATOR) Blocks 1 and 2.

Northrop Grumman’s AN/TPS-80 G/ATOR is a multi-mission active electronically scanned array (AESA) radar that

provides comprehensive real-time, 360° situational awareness.

To date, eight AN/TPS-80 G/ATOR production systems have been delivered to the Marine Corps. In early 2017,

Northrop Grumman delivered six low-rate initial production systems. The first systems incorporating gallium

nitride (GaN) technology were delivered ahead of schedule in July 2018 and were used for development test

(DT) 1E1, DT1E2 and IOT&E.

http://www.semiconductor-today.com/news_items/2019/may/wolfspeed-310519.shtml


IOT&E is a rigorous phase of testing that a new system undergoes to determine that it is operationally effective

and suitable for fleet introduction. The milestone demonstrates viability and suitability of the system, and

completion indicates the Marine Corps is ready to operate and field G/ATOR Blocks 1 and 2 in their current

configuration. The commitment of both the Marine Corps and G/ATOR team to deliver an operationally

effective, 360° AESA radar system will ensure that warfighters can detect – and take action against – complex,

modern threats, Northrop Grumman says.

“Through our close partnership with the Marine Corps, we have been able to successfully achieve the IOT&E

milestone and begin fielding this radar system with unrivaled mission capability to operational units,” says

Christine Harbison, vice president, land and avionics C4ISR, Northrop Grumman. “We are proud to deliver

hardware-enabled, software-defined advanced ground radar systems that meet our customer’s mission needs,

protect the warfighter in a rapidly changing threat environment, and have significant margin for capability

growth.”

Nitrogen-polar gallium nitride current-aperture vertical electron transistor SemiconductorToday

Researchers based in the USA have reported the ‘first demonstration’ of a nitrogen-polar (N-polar) gallium

nitride (GaN) current-aperture vertical electron transistor (CAVET) [Saba Rajabi et al, IEEE Electron Device

Letters, published online 1 May 2019]. The device also achieved a blocking electric field of 2.9MV/cm.

The use of N-polar structures allows the use of an aluminium gallium nitride (AlGaN) back-barrier to induce a

two-dimensional electron gas (2DEG) in an overlying GaN channel layer. This reverses the usual structure in Ga-

polar material where a top AlGaN barrier layer is used. A back-barrier structure is attractive in radio-frequency

power applications such as amplifiers to reduce power losses. Another attractive feature is that Ohmic metal

contact is not impeded in the presence of a top barrier.

CAVETs combine a lateral channel and a vertical voltage-blocking structure that allows higher electric fields and

eliminates dispersion/current collapse under pulsed operation.

University of California Davis (UCD), University of California Santa Barbara (UCSB) and Stanford University used

metal-organic chemical vapor deposition (MOCVD) epitaxial growth on c-plane sapphire, beginning with an

unintentionally doped (UID) GaN buffer layer. The structure (Figure 1) continued with 200nm n+-GaN drain and

200nm UID n-GaN drift layers.

The current-block layer (CBL) regions were formed using selective-area implantation of magnesium ions (Mg2+)

into the drift layer. The implantation was followed by annealing at 1280°C for 30s in nitrogen atmosphere.

According to the researchers, the annealing did not need a cap layer due to the thermal stability of the N-polar

GaN. Such cap layers can have detrimental effects since they can crystallize, making removal difficult. “This is

another advantage of N-polar GaN that can play a very important role in implantation-based device

technology,” the researchers write.

After the implantation, further layers were grown at 1160°C: 3nm graded AlGaN, 1nm AlN, 150nm n-GaN, and

40nm n+-GaN. Secondary-ion mass spectrometry (SIMS) showed that the AlN barrier was effective in blocking

out-diffusion of Mg atoms from the CBL into the regrown layers. Such out-diffusion would negatively impact the

2DEG region that forms near the AlN/n-GaN interface in the regrown structure.

http://www.semiconductor-today.com/news_items/2019/may/ucd_300519.shtml


Fabrication began with chlorine-based inductively coupled plasma (ICP) etch of isolation 400nm-high mesas.

Reactive-ion etch (RIE) exposed the gate and access regions of the transistor. The gate dielectric and surface

passivation consisted of 20nm of MOCVD silicon nitride.

The ohmic contact regions were exposed with fluorine-based RIE through the silicon nitride. The source/drain

ohmic contact metal stacks were annealed titanium/aluminium/nickel/gold. The gate metal was nickel/gold.

The gate electrode was split in two to minimize gate-drain leakage and to maximize electrostatic control over

the source current. The gate length (Lg) and width were 566nm and 150μm, respectively. The gate-source (Lgs)

distance was 2μm; the gate-aperture (Lga) distance was 1.3μm. The aperture gap (Lap) was 2μm.

With the gate at 0V, the maximum drain current density was 1.68kA/cm2; the specific on-resistance was

2.48mΩ-cm2. The current density and specific on-resistance were normalized according to the source contact

lengths and source-source distance (11.3μm) and the device width (150μm), giving an area of 1.7x10-5cm2. The

current pinched-off when the gate was at -8V. The on/off current ratio was 106.

Pulsed measurements showed no dispersion from DC performance. The team attributed this to the vertical

structure whereby the peak electric field is situated deep the drift region, away from the surface traps that

impact pulsed performance.

Figure 1: (a) Sketch of N-polar AlN/GaN-based CAVET. (b,c) Band diagrams through aperture (A-A’) and CBL (B-

B’) regions, respectively.


With the gate pinched-off, the breakdown voltage (Figure 1) was 58V for a leakage of 1mA/cm2. The

researchers estimate the peak electric field at 2.9MV/cm. The researchers claim this as the “first evidence of

such a high breakdown field achieved in vertical N-polar GaN transistors.”

Figure 2: Three-terminal breakdown with the gate at pinch-off (-8V). (b) Gate dielectric breakdown test with

floating source. (c) n-CBL-n test structure measurement.

Experiments on various test structures indicated that the breakdown occurred via punch-through in the current-

block layer, not the gate dielectric. The team believes that the CBL could be improved with a more uniform,

thicker implantation profile. Thicker, lower-doped drift regions also would enable increased breakdown

voltages. The researchers say that there is progress towards growing such thicker drift regions on N-polar GaN

with lower dislocation density generation, as needed for high breakdown voltages and low leakage.

MMIC market growing at 10.6% CAGR from $7.7bn to $12.7bn by 2024 SemiconductorToday

The monolithic microwave integrated circuit (MMIC) market will grow at a compound annual growth rate

(CAGR) of 10.6% from $7.7bn in 2019 to $12.7bn by 2024, according to a report from Global Information Inc.

Factors driving growth include: increased demand from the smartphone industry; increasing adoption of E-band

frequencies to meet the growing bandwidth requirements of the space, defense and wireless communication

infrastructure sectors; and rising defense spending of countries globally.

http://www.semiconductor-today.com/news_items/2019/may/gii-200519.shtml


Power amplifier segment to hold largest market share

Most power amplifiers are designed for a specific application producing a specific type of signal, signal

modulation scheme, and a set of specifications such as frequency range, gain (dB), gain flatness (dB), supply

voltage (VDC), power decibels (dB-milliwatt), and package type.

MMICs developed using GaN offer high input power survivability of 40dBm, potentially eliminating the

requirement for a power limiter in broadband communication, electronic warfare (EW) instrumentation or radar

applications.

Growth of this segment can be attributed to the increased use of power amplifiers in defense, automotive,

smartphone and wireless communication applications, driven by the continuously growing demand for high data

transfer rates in communication systems.

GaN material segment to grow at highest CAGR

As well as its high-brightness emission in optoelectronics, gallium nitride (GaN) is an emerging alternative to

silicon due to its high power efficiency, superior high-frequency handling capacity and its flexibility to be used

with various substrates such as silicon, sapphire and silicon carbide (SiC). Since it is a hard and mechanically

stable material with a wide bandgap and high heat capacity and thermal conductivity, MMICs developed using

GaN offer large bandwidth, improved power density and high efficiency to support the future cellular

infrastructure such as 5G for the mobile base-station transmitters.

E-pHEMT device segment to grow fastest

Enhancement-mode pseudomorphic high-electron-mobility transistors (E-pHEMTs) offer superior output power

and high efficiency with bias voltages of less than +3VDC. For commercial communication systems, E-pHEMTs

offer a combination of high gain, low noise and wide dynamic range in high-linearity MMIC applications. These

transistors can economically provide superior electrical performance in very high frequency (VHF) and ultra high

frequency (UHF) wireless communication bands commonly associated with technologies such as gallium

arsenide (GaAs) MESFETs and depletion-mode pHEMTs.

Asia Pacific to be largest market by region

Asia Pacific was the largest MMIC market by geographic region in 2018. The main growth drivers are the

expanding cellular infrastructure in the region and the increasing number of telecom equipment shipments in

countries such as China and India. Japan has been a dominant player in the global semiconductor industry since

the 1960s, while the strategy of China is to develop the highest-performance products at the lowest cost, which

has helped it gain a large share of the Asia Pacific MMIC market. The increased production of electronic devices

in the region due to the low manufacturing cost and availability of cheap labor is another growth driver. Rising

demand for smartphones, digital televisions, automobile electronics, and electro-medical devices in the Asia

Pacific region is expected to contribute to growth of the MMIC market in the region.

Key players in the MMIC market are cited as Analog Devices (USA), NXP Semiconductor (Netherlands), MACOM

(USA), Qorvo (USA), Skyworks Solutions (USA), Broadcom (USA), Infineon Technologies (Germany), Maxim

Integrated (USA), Mini-Circuits (USA), OMMIC (France), WIN Semiconductors (Taiwan), United Monolithic

Semiconductors (UMS) (France), Custom MMIC Design Services (USA), Microarray Technologies (China),

VectraWave (France), BeRex (South Korea), and Arralis (Ireland).


EPC: Ahead Of The Pack CompoundSemiconductor

For EPC chief executive, Alex Lidow, this year's PCIM Europe 2019 has been all about applications. Presenting

myriad enhanced-mode GaN FETs and ICs in end-products, the company is making a big play for 48 V DC-DC

power conversion in advanced computing and automotives.

“The market that we are making a full-frontal attack on, is silicon at 48 V input,” he says. “We can get higher

performance from GaN at a lower cost and with less design time... just think what it's going to be like in a few

years.”

“It's been a race and GaN has always been in front on performance but not on price,” he adds. “But now we're

in front on performance and price, and we're also accelerating; silicon's stuck in the mud.”

In recent years, EPC has been introducing ever-smaller, cheaper and higher-performing chips. Recently

delivering 100V eGaN FETs for 48V DC-DC conversion in servers and automotives, as well as automotive-

qualified 80 V eGaN FETs for lidar applications in autonomous vehicles, Lidow says device costs now rival those

of silicon chips.

“We've shrunk the die so much that, for the same ratings, we price our products at or below silicon [prices],” he

says. “Price comparisons with silicon MOSFETS at a range of performance levels show that whether we're at low

or high volumes, we're priced at the below average point.”

“And of course, the performance of GaN devices is so much superior to silicon MOSFETs at 48V,” he adds. “So

our devices are smaller and more efficient than silicon MOSFETs, yet the same price, so what's not to like?”

Market moves

With market penetration a priority, Lidow has his sights set on data-centre and automotive applications.

Following the success of the Open Compute Project - an organisation that shares designs of data-centre

products - engineers are moving to 48 V rack-level power distribution systems to boost energy efficiency of the

latest high performance computers and servers for data centres.

“We have this movement towards 48V... and today the preferred solutions are LLC-converter and buck

converter [power conversion] topologies,” highlights Lidow. “And here, I will say with all due modesty, our

products have swept all the new designs. Almost all of this is coming out of Asia, and it's a big deal for us.”

Meanwhile, the automotive industry continues its shift from 12 V to 48 V electrical distribution buses,

particularly in mild hybrid vehicles, to handle power steering, power brakes, air conditioning, suspension, high-

intensity headlamps, start-stop systems and more. What's more, new applications such as autonomous vehicles

equipped with sensors, lidar and radar are also emerging.

As such, Tier 1 automotive suppliers are busy developing 48 V electrical systems, as well as bi-directional

systems to support both 48 V and 12 V legacy accessories.

“Given all of this, automotives is huge for us,” says Lidow. “For example, the minute you go to even a mild

hybrid vehicle, you have more electrical components drawing more and more power.”

https://compoundsemiconductor.net/article/107189/EPC_Ahead_Of_The_Pack


“We have 80 V and 100 V FETs auto-qualified for DC to DC, lidar and headlamp applications and we're also

designing into infotainment and radar systems,” he adds. “There's a heavy design effort here right now and the

market will really be starting to reach volume [production] in 2021.”

Indeed, for the EPC chief executive, the real action for GaN still lies at 400 V and lower, where the

semiconductor's high frequency and switching speeds are imperative for applications such as lidar. “[Compared

to lower voltages], the 600 V GaN market is a crowded field right now and has key vulnerabilities,” he says. “For

starters, it's not such a performance-sensitive market, and both silicon and silicon carbide are also gunning for

that 600 V node.”

At the same time, he highlights how remote control electronics are enabling the use of multi-level converters to

hit the higher voltages. Case-in-point, at this year's PCIM, EPC demonstrated a 400 V input power factor

correction circuit made from 200 V devices stacked in series.

“In this way you can pick up the higher power density at a lower cost,” he says. “So at these higher voltages, the

threats for GaN are coming in from all directions... I'm not saying this isn't a valid market but it's going to be a

difficult slog.”

So where next for EPC and GaN? In short, integration and monolithic GaN ICs.

In March this year, EPC revealed a monolithic half-bridge GaN transistor with level shifters and drivers

integrated onto the chip. The transistors are currently with alpha-customers and Lidow expects to launch

devices towards the end of this Summer.

What's more, he believes this latest IC marks the beginning of a new era for GaN power components. “Today we

see power components as transistors or diodes but I predict this [monolithic device] will redefine what a power

components is,” he says. “And I will also say that in five years, I doubt we will be launching discrete GaN

transistors at all; instead we'll be launching power products that have features and functions.”

OPTOELECTRONICS

Seoul Semiconductor files patent suit against European distributor of MEGAMAN lighting products SemiconductorToday

South Korean LED maker Seoul Semiconductor Co Ltd has filed a lawsuit in Germany in the District Court of

Düsseldorf asserting that European LED lighting distributor Leuchtstark Vertriebs GmbH is selling a ‘MEGAMAN’

brand lighting product that infringes two of its LED patents. MEGAMAN is an Asian-based LED lamp brand. Seoul

is currently investigating Leuchstark’s OEM/ODM manufacturers as well as other distributors.

The asserted patents relate to one of Seoul’s LED light extraction patent portfolios. In December, Seoul

successfully enforced a patent in the field of LED light extraction technology, and the District Court of Düsseldorf

ordered an injunction against sales of the accused Everlight products as well as a recall of any such products sold

after 13 July 2012.

Seoul holds rights to more than 14,000 LED patents, and has notified 90 companies regarding TVs, cell phones,

lighting and automobiles of patent infringements in the past year. Seoul has successfully enforced 62 patents in

eight countries in the past five years.

http://www.semiconductor-today.com/news_items/2019/jun/seoulsemi-050619.shtml


“Respecting intellectual property is essential to establish a fair competition business culture,” says Nam Ki-bum,

executive VP of the Lighting Department at Seoul Semiconductor. “We will take all necessary legal actions

against companies that have suspicions of infringing our patents or of unlawful access to our trade secret by

luring employees, as we have done against Everlight.”

Klaran launches 60mW UVC LED and reactor prototype for water disinfection SemiconductorToday

Crystal IS Inc of Green Island, NY, USA, an Asahi Kasei company that makes proprietary ultraviolet light-emitting

diodes (UVC LEDs), says that its Klaran product line has gained a new 60mW UVC LED in its water disinfection

(WD) series.

In an advanced prototype reactor, the 60mW LED has demonstrated effective and affordable water treatment

at flow rates up to three liters per minute, with disinfection rates comparable to NSF/ANSI 55 Class ‘A’, says the

firm. Klaran’s existing WD series LEDs and water treatment reactors are used to treat point-of-use (PoU) water

at flow rates up to two liters per minute and at disinfection rates comparable with NSF/ANSI Class ‘B’.

The new reactor, which is expected to be ready for market in early 2020, incorporates a user-replaceable LED

‘engine’ to address both the different market performance requirements and alternate business revenue

models of the commercial water industry. Similar to Klaran’s other WD series devices, the new LED is priced at

under 25 cents per mW. “The introduction of our new 60mW LED marks another milestone in proving that UVC

LEDs can affordably deliver the performance needs of the commercial and consumer point-of-use markets,” says

Eoin Connolly, VP for Klaran.

Klaran’s expanding portfolio of products enable manufacturers and distributors of point-of-use water products

to reduce their total cost of ownership by addressing maintenance issues, such as annual replacement and

unplanned service, related to traditional UVC technologies, says the firm. “An unplanned UV lamp failure can

quickly cost hundreds of dollars to a service provider, making a serious impact on profit margins,” notes

Connolly. “Our rigorous testing of thousands of Klaran devices and ISO 9001 quality system provide the data-

driven proof in the reliability and performance of our Klaran products,” he adds.


Indium gallium nitride platelets for green and red light-emitting diodes SemiconductorToday

Lund University and RISE Research Institutes in Sweden have developed indium gallium nitride (InGaN) platelet

arrays as a basis for green and red light-emitting diodes (LEDs) [Zhaoxia Bi et al, Nano Lett., published online 2

April, 2019]. The researchers used the platelets to achieve quantum well (QW) regions with higher indium

content with less compressive strain from lattice mismatching. “The large strain has a direct impact on the

crystal quality of the QWs, potentially introducing plastic crystal deformation during growth and then leading to

a dislocation formation,” the team explains.

High strain in InGaN heterostructures also leads to large piezoelectric fields, which reduce the efficiency of the

electron-hole recombination processes that are needed for photon emission – a mechanism called the

‘quantum-confined Stark effect’ (QCSE).

Strain effects severely reduce the performance of red and green InGaN-based LEDs, relative to blue devices that

can reach 80% external quantum efficiency. By using the InGaN platelets, lower strain in InGaN QWs with high

indium content should be achieved due to the smaller lattice mismatch. Higher indium content narrows the

bandgap, increasing the wavelength.

The platelet growth technique combined selective-area metal-organic vapor phase epitaxy (MOVPE) and

reformation to convert InGaN pyramid structures into c-plane oriented platelets. The selective-area epitaxy was

on (0001) GaN-on-silicon templates, using silicon nitride masking with 100nm-diameter holes at 1μm pitch. The

platelets are 100-200nm high and extend laterally a few hundred nanometers.

The reformation process consisted of 1070°C annealing in ammonia (NH3) and InGaN regrowth to create a

smooth top surface. The annealing did not affect the {10-11} pyramid side facets, which remained smooth after

the thermal processing.

The researchers explain: “The surfaces of {10-11} planes are N-terminated. N atoms at the surface are supposed

to bond with H atoms cracked from NH3, which can be a reason for the stable {10-11} planes during the

annealing.”

The regrowth included an intermediate InGaN layer with a low V/III ratio of 700 (close to the limit for In/Ga

droplet formation). The aim of the intermediate layer was to reduce pit formation in the c-plane surface. The

researchers suggest that the metal-rich conditions on the growth plane gives a longer adatom diffusion length,

flattening the initially rough surface.

The indium content of the intermediate layer was estimated to be less than 5%. The technique was successful in

removing pits from In0.09Ga0.91N platelets, but there remained some pits in In0.18Ga0.82N structures. This

residual pitting was attributed to the larger lattice mismatch with the intermediate layer. The top InGaN layer

was 40-50nm thick.

Comparison of photoluminescence and energy-dispersive x-ray analysis suggested that the InGaN below the

intermediate layer had higher indium content fluctuations compared with the InGaN above. Photoluminescence

analysis tends to overestimate indium content when there are large fluctuations.

The researchers found that growth of InGaN quantum wells on the InGaN platelets had enhanced indium

incorporation, probably due to reduced compressive strain relative to wells grown on pure GaN.

http://www.semiconductor-today.com/news_items/2019/may/lunduniversity_230519.shtml


The InGaN platelets had narrow photoluminescence peaks: 107meV and 151meV full-widths at half-maximum

(FWHMs) for In0.09Ga0.91N and In0.18Ga0.82N, respectively. These platelets were used for green and red LEDs,

respectively.

Figure 1: (a, e) Cross-sectional high-angle annular dark-field scanning transmission electron microscope

(HAADF-STEM) images of single QW samples. The white arrow in panel e indicates dislocation. (b, f) Magnified

HAADF-STEM images close to periphery and (c, g) high-resolution TEM images in middle of QWs. (d, h) CL

spectra measured at 10K. Inset: SEM images and corresponding monochromatic CL images with QW emission.

CL images recorded in energy windows of (d) 1.80−2.50eV and (h) 1.85−2.35eV.

Cathodoluminescence (CL) spectra under electron-beam excitation showed a QW peak in the emission at 2.17eV

(in the yellow range) for the In0.09Ga0.91N platelet and 1.95eV (red) for In0.18Ga0.82N (Figure 1). The

researchers report that the QW was slightly thicker on an In0.18Ga0.82N platelet – 5.8nm, compared with

4.5nm. The team suggests the thicker well increases the quantum-confined Stark effect, red-shifting the

emission.

The indium content of the well could also be higher on the higher-indium-concentration platelet, narrowing the

bandgap. The higher indium content could be the result of reduced ‘indium pulling’ compared with the lower-

indium-concentration platelet.

For LEDs, a ~200nm p-InGaN contact layer was added to platelets with quantum wells (Figure 2). The n-contact

was through the n-GaN buffer. Electrical isolation was achieved with 30nm atomic layer deposition (ALD)

aluminium oxide (Al2O3) passivation and spin-coated/planarized polymer spacer material. The spacer was also

used as an etch mask for removal of the Al2O3 from the top of the p-GaN contact. The contact metal was

circular in form with 360μm diameter, covering around 1.2x105 platelets.


Figure 2: (a) Schematic of InGaN platelet LEDs. (b, c) EL spectra obtained at different current injection levels

for green and red LEDs on In0.09Ga0.91N and In0.18Ga0.82N platelets, respectively. Current density

normalized to QW rather than contact area.

Electroluminescence (EL) from the LEDs gave green (2.30eV) and red (1.98eV) peaks for In0.09Ga0.91N and

In0.18Ga0.82N platelet structures, respectively. The corresponding FWHM linewidths were 210meV and

150meV.

Osram launches its first quantum dot LED SemiconductorToday

In booth #1701 at the LIGHTFAIR International 2019 trade show in Philadelphia, PA (19–23 May), Osram Opto

Semiconductors GmbH of Regensburg, Germany is showcasing its first quantum dot (QD) LED.

Due to their very small size, the light that is re-emitted when blue LED light hits nanoparticles depends on their

size: QD particles that are roughly 3nm in size produce green light, while particles about 7nm emit red light.

Osram is using such tunable light conversion technology for the first time in its new Osconiq S 3030 QD mid-

power LED, which will lead to more QD LEDs for the general lighting market in the future. The Osconiq S 3030

QD was specially developed to enable users to design luminaires with high efficacy and color rendering for area

lighting and downlight applications.

When manufacturing conventional white LEDs, the main objectives are efficacy and product quality. Achieving

both at the same time is particularly challenging, especially with very high color rendering indexes (CRI), says

Osram. The advantage of using quantum dots is that the existing LED manufacturing processes remain the same.

QDs are simply used instead of conventional phosphors when the converter material is applied.

More than a year ago, Osram acquired Pacific Light Technologies (PLT), which develops and manufactures

optical nanomaterials. Osram says that the PLT QD technology is enabling it to begin to close the efficacy gap

that exists between CRI 80 and CRI 90 LEDs today. The new Osconiq S 3030 includes a specially developed QD

phosphor solution that enables CRI 90 to achieve an efficacy value of 173lm/W at 3000K – which is claimed to

http://www.semiconductor-today.com/news_items/2019/may/osram-210519.shtml


be a best-in-class value for 0.2W high-performance LEDs. The compact dimensions of 3.0mm x 3.0mm and the

low thermal resistance enable simple system design. The Osconiq S 3030 QD is also available in various color

temperatures, from 2700 to 6500K.

Osram says that another unique feature of the PLT QD technology is that the quantum dots are encapsulated to

protect them from moisture and other external influences that pose the greatest risk to the functionality of an

LED. The special encapsulation technology allows the QDs to reliably master the demanding conditions of on-

chip operation within the LED component, the firm adds.

Plessey enters into long-term micro-LED supply agreement with Vuzix SemiconductorToday

An exclusive display device design and long-term supply agreement will support the development and

production of next-generation augmented reality (AR) products and solutions combining the micro-LED light

source technology of UK-based Plessey with the expertise and IP in smart glasses and essential optics

technologies of Vuzix Corp of Rochester, NY, USA.

Vuzix has already developed an evolving family of smart glasses culminating in the Vuzix Blade, a next-

generation smart display with a see-through viewing experience via its proprietary waveguide optics. Formed

from glass with precision nanostructures, the waveguide enables users to see high-resolution computer-

generated graphics, images and information superimposed over images from the physical or real world.

Plessey says that its micro-LED solution will simplify existing smart glasses’ complex optical system of red, green

and blue light sources and their additional optics by replacing it with a single self-emitting display that has

integrated micro-optical elements. Size, weight and power reduction are key considerations in the AR wearables

market. Existing light source systems have considerable losses all the way through to the waveguide and the

optical systems around them are bulky and complex, whereas an emissive micro-LED has simple optical

requirements, allowing a much smaller footprint with minimal system losses by placing the light source directly

in front of the waveguide.

“Micro-LED technology represents a key part of the solution needed to bring the form and functionality of Vuzix

next-generation smart glasses to the look and feel of fashion forward glasses,” believes Vuzix’s president & CEO

Paul Travers.

“By overcoming the difficulties of manufacturing micro-LEDs on a commercial scale, Plessey is playing a central

role in providing next-generation technology to the augmented reality and display markets,” says Plessey’s

president of corporate and business development Mike Lee.

Ultraviolet aluminium gallium nitride shell nanowire light-emitting diodes SemiconductorToday

The National Institute of Standards and Technology (NIST) and University of Colorado in the USA have reported

aluminium gallium nitride/gallium nitride (AlGaN/GaN) shell/core nanowire light-emitting diodes (LEDs) that

demonstrated ~5x the light output compared with GaN/GaN nanowire devices [Matt D Brubaker et al,

Nanotechnology, vol30, p234001, 2019].

Developing ultraviolet LEDs such as the 365nm wavelength from the AlGaN/GaN device are seen as being useful

for spectroscopy, photopolymer curing, water purification and medical disinfection. Some of these applications

need short ‘deep’ UV wavelengths less than 300nm. Nanowire structures might be useful in boosting the pitiful

efficiencies (mostly less than 10%) in high-aluminium-content AlGaN LEDs based on conventional technology.

http://www.semiconductor-today.com/news_items/2019/may/plessey-210519.shtml


First, ordered arrays of nanowires were grown using plasma-assisted molecular beam epitaxy (PAMBE) on

nitrogen-polar GaN/AlN templates on (111) silicon with a silicon nitride mask. The holes in the mask for

nanowire growth were 80-240nm diameter with 300-10,000nm pitch. The silicon-doped n-GaN cores were

grown at 860°C substrate temperature. The core length was around 2μm. The ~40nm-thick silicon-doped

Al0.09Ga0.91N shell was grown at 700°C.

Photoluminescence spectra measured at 5K suggested that the Al mole fraction of the shell tip decreased with

nanowire diameter. By contrast, reducing the pitch increased Al concentration. The decrease in Al content at the

nanowire tip was related to reduced mobility of the atoms at the growing tip, compared with Ga.

The Al content of the main shell of the nanowire stems was more difficult to determine, probably due to non-

radiative recombination, surface states and defects. The researchers used emissions from excitons (bound

electron-hole states) to estimate Al content. Smaller-diameter nanowires were found to have higher-Al-content

shells. Smaller pitch arrays had low Al concentration.

The nanowire growth process was modified to include doping for p-i-n LEDs. The n-GaN core region was grown

to a height of 3.3μm pitched at 5μm. Shell growth was initiated with 15nm n-GaN followed by ~85nm intrinsic

AlGaN, ~285nm p-AlGaN and ~5nm heavily doped p++-AlGaN.

The LED p-contact electrode was constructed by 20nm/200nm nickel/gold deposition at normal incidence,

followed by 200nm gold at 45°. This covered one side of the wires with metal while the other side allowed light

extraction. The n-side current flow was through the buffer with electrical isolation provided by the silicon nitride

nanowire growth mask.

Figure 1: Core–shell p–i–n nanowire LED characteristics comparing AlGaN/GaN heterojunctions and GaN/GaN

homojunctions. (a) Scanning electron micrograph of post-metallization AlGaN/GaN core–shell LEDs, with inset

pre-metallization single nanowire. (b) Current-voltage characteristics and (c) EL spectra for 25 nanowire LEDs.

(d) EL images for 4 nanowire LEDs are shown in the figure. GaN p–i–n EL intensities multiplied by factor of

three. (e) Peak emission wavelength and (f) integrated intensity versus current for various core diameters.


The researchers compared the performance of the AlGaN/GaN heterojunction LEDs with GaN/GaN

homojunction nanowire devices previously reported by the group (Figure 1). The turn-on voltage of the

AlGaN/GaN LEDs was higher than for GaN/GaN, “likely related to the reduced electron overflow current and

increased barrier to hole injection expected for higher Al mole fractions,” according to the team.

Subjecting the AlGaN/GaN LED to prolonged current injection seemed to have an electrical annealing effect on

the p-contact, giving increased electroluminescence (EL) intensity and lower series resistance. The researchers

comment: “Further development of optimized p-contact metallization and annealing processes are expected to

reduce burn-in effects and improve overall device performance.”

The EL from the AlGaN/GaN was around 365nm wavelength, close to the band edge of GaN. This was in contrast

to the GaN/GaN LEDs, which emitted around 380nm, corresponding to donor-acceptor-pair (DAP)

recombination from electrons injected into the p-GaN shell, according to the researchers. The team also

suggests that GaN core emissions could be reabsorbed in the GaN shell, unlike with the wider-bandgap AlGaN.

The 380nm emission and 365nm reabsorption effects are stopped by the wider-bandgap AlGaN, which is also

commonly used as an electron-blocking layer in standard GaN LEDs. The researchers report that the integrated

EL intensity in the AlGaN/GaN nanowire LEDs was around 5x that of the GaN/GaN reference for a given current

injection.

Leti develops CMOS-driven micro-LEDs with simplified transfer process that eliminates TFT backplane SemiconductorToday

On 14 May during Display Week 2019 in San Jose, CA, USA, micro/nanotechnology R&D center CEA-Leti of

Grenoble, France has presented a paper on new technology for fabricating high-performance gallium nitride

(GaN) micro-LED displays for applications ranging from smart watches to TVs with no size limit.

The approach fabricates elementary units of all-in-one red, green, blue (RGB) micro-LEDs on a CMOS driving

circuit, and transfers the devices to a simple receiving substrate. The units are fabricated with a full

semiconductor, wafer-scale approach.

“This new process, in the proof-of-concept stage, paves the way to commercial, high-performance micro-LED

displays,” reckons François Templier, CEA-Leti’s strategic marketing manager for photonic devices. “The CMOS-

based approach provides higher-brightness and higher-resolution micro-LEDs and is a game changer for very

large TVs,” he adds.

While they promise exceptional image quality and better energy efficiency than existing liquid crystal display

(LCD) and organic light-emitting diode (OLED) technologies, micro-LED displays currently face significant barriers

to commercialization.

One of the biggest challenges is improving the performance of the driving electronics, which require more

power to deliver brighter images and more speed to support continuously increasing demands for high display

resolution. Faster electronics are required to power millions of pixels in a fixed-frame time in micro-LED

displays, but existing thin-film transistor (TFT) active-matrix driving display technology cannot provide the

necessary current and speed.

CEA-Leti’s new approach fabricates CMOS-driven, high-performance GaN micro-LED displays with a simplified

transfer process that eliminates the use of the TFT backplane. RGB micro-LEDs are stacked directly onto a micro-

http://www.semiconductor-today.com/news_items/2019/may/leti-150519.shtml


CMOS circuit, and each unit is transferred onto a simple receiving substrate. Then, the RGB micro-LEDs and the

backplane are fabricated on a single semiconductor line.

In addition to increasing power and driving speed – and improving display performance – this process avoids

several costly steps needed with existing technology to make electrical and mechanical contacts between micro-

LEDs and the receiving substrates.

New technique could pave way to simple color tuning of monolithically integrated GaN LEDs SemiconductorToday

A team at Lehigh University, West Chester University, Osaka University and the University of Amsterdam has

demonstrated a new technique that could enable simple color tuning of gallium nitride (GaN)-based LEDs simply

by changing the time sequence at which the operating current is provided to the device (ACS Photonics, ‘Color-

Tunablility in GaN LEDs Based on Atomic Emission Manipulation under Current Injection’).

Notably, the technique is compatible with current LEDs that are at the core of commercial solid-state LED

lighting. “This work could make it possible to tune between bright white and more comfortable warmer colors in

commercial LEDs,” says Volkmar Dierolf, Distinguished Professor and Chair of Lehigh’s Department of Physics,

who worked on the project.

Lead author Brandon Mitchell is a former graduate student in Dierolf's lab, now an assistant professor in the

Department of Physics and Engineering at West Chester University in Pennsylvania.

In existing active LED displays, different colors are produced by three to four individual LEDs placed close to

each other that create the different fundamental colors needed to produce the full color spectrum.

“We demonstrate that this can be achieved by a single LED,” says Dierolf.

“We show that is possible to attain red, green and blue emissions originating

from just one GaN LED structure that uses doping with a single type of rare-

earth ion, europium (Eu),” he adds. “Using intentional co-doping and energy-

transfer engineering, we show that all three primary colors can emit due to

emission originating from two different excited states of the same trivalent

Eu3+ ion (620nm red/orange and 545nm green) mixed with near-band-edge

emission from GaN centered at ~430nm (blue/violet). The intensity ratios of

these transitions can be controlled by choosing the current injection

conditions such as injection current density and duty cycle under pulsed

current injection.”

In other words, the team achieved color-tunability in a single GaN-based LED through the manipulation of the

emission properties of an atomic-type dopant.

Graphic: Top row is a GaN:Eu LED, which can be tuned from red-yellow due to red and green light mixing from

different Eu states. Middle and bottom rows are of a GaN:Eu LED with additionally added Si/Mg, which adds

blue emission. Each picture is under a different current injection/filtering condition. Credit: West Chester

University.

“The main idea of this work - the simultaneous active exploitation of multiple excited states of the same dopant

- is not limited to the GaN:Eu system, but is more general,” notes Mitchell. “The presented results could open up

a whole new field of tunable emission of colors from a single dopant in semiconductors, which can be reached

by simple injection current tuning,” he adds.


The research could benefit those looking for more comfortable ‘warmer’ white light from LEDs. “It could pave

the way for monolithic integration for simple color tuning of a light bulb,” says Dierolf. “It would also be

beneficial for micro-LED displays, since it allows for higher density of pixels.”

The materials used in previous research on color tunable LEDs did not allow for easy integration with current

LED technology, he adds. This work is compatible with existing GaN-based LEDs that are at the core of

commercial solid-state LED lighting.

Rise of LED Lighting For Cars Driven By Energy Efficiency CompoundSemiconductor

The approximately $35 billion market for automotive lighting is estimated to see just under 5 percent year on

year growth in 2019, according to a new report by Future Market Insights. While passenger cars have

significantly driven the LED Automotive Lighting Sales, bright prospects have been foreseen for sales in electric,

in line with the rising trend of vehicle electrification.

Nearly 60 percent of the automotive lighting systems installed are of headlights/front lights, which collectively

capture more than 3/4th of the market revenue, with rear lights. Fog lights are gradually gaining ground in front

and rear lighting systems, which is likely to shape the overall performance of automotive lighting market, as

indicated by the report.

Lightweight automotive components have been a trendsetter over the past decade, will push the demand

growth of lightweight automotive lighting in parallel. This growth forecast is predominantly owing to increasing

vehicle electrification and surging demand for high-performance, fuel efficient vehicles.

Halogen lamps continue to reign supreme, holding more than 65 percent share in the automotive lighting

market. In line with tightening vehicle emission standards that demand reduced weight and improved fuel

efficiency, the automotive lighting market will observe strong emergence of LED. Superior endurance and high

energy efficiency are projected to provide an impetus to LED popularity over halogen and HID counterparts. The

report envisages a preeminent push to LED automotive lighting from manufacturers of premium class vehicles.

Enhanced aesthetic appeal of vehicles with innovative lighting features will remain a priority strategy for leading

automakers and OEMs. However, lighting technology innovators in collaboration with prominent market players

are also strategizing on introducing economic range products, which is cited as another factor providing a strong

push to LED automotive lighting products.

While compact and mid-size passenger car manufacturers remain prime consumer of automotive lighting

solutions, the report indicates that this demand growth will be spectacular in EVs over the coming years. Hybrid

EVs will further account for a considerable demand share in automotive lighting market. Moreover, billowing

sales of motorcycles, particularly in developing economies, will bolster installations of a wide range of

automotive lighting in the two-wheelers segment, says the report.

In a fairly consolidated competitive landscape of automotive lighting market, a majority of players are based in

North America, Europe, and China. Automotive lighting market leaders such as Koito Manufacturing, Valeo SA,

Magneti Marelli, Hella, and Stanley Electric continue to dedicate a majority of investments in strategic

acquisitions and new product launches.

Valeo recently acquired a Japanese automotive lighting manufacturer, Ichikoh Industries, Ltd. Expansion has

also been among the key developmental strategies in the competitive landscape of automotive lighting market.

On the other side, Tier 2 companies including Osram, Varroc Group, Robert Bosch, LG Lightings, and Hyundai

https://compoundsemiconductor.net/article/107409/Rise_Of_LED_Lighting_For_Cars_Driven_By_Energy_Efficiency


Mobis are focusing on collaborative ventures that prominently target product innovations and new launches in

automotive lighting space.

In the latter half of 2018, Fiat Chrysler Automobiles inked a collaborative agreement over the sale of their

automotive components business - Magneti Marelli to the Japanese supplier CK Holdings. (Calsonic Kansei

Corporation's holding company). Osram has been actively introducing new automotive lighting product lineups

in the market.

While Europe retains the top consumer title in automotive lighting landscape, the report projects significant

growth potential for automotive lighting market in emerging Asian countries. Automakers, OEMs, and other

lighting product manufacturers will capitalise on a series of untapped opportunities particularly in East Asian

market, attributed to soaring automotive sales, elevating acceptance for EVs and HEVs, and more importantly,

improving purchasing power of consumers. East Asia is likely to represent just-under a third of the global

automotive lighting market value, towards 2019 end.

OTHER

Newport Wafer Fab completes multi-million-pound refinancing deal to new fund equipment and plant SemiconductorToday

Newport Wafer Fab (NWF), the UK’s 200mm compound semiconductor wafer foundry, has completed a multi-

million pound refinancing deal, involving a restructure of existing Welsh Government loans and a new asset

finance facility from HSBC UK.

The deal includes the early settlement of deferred

consideration, the purchase of specialist back-end-of-line

equipment to broaden the foundry’s manufacturing

capabilities, and a £3m contribution to a new combined

heat and power (CHP) plant designed to reduce utility

costs by over £1.5m per annum.

NWF was acquired by private investors in September 2017

from Germany’s Infineon Technologies AG (which

acquired the fab on buying US-based International

Rectifier Corp at the beginning of 2015).

NWF is a critical component of CS Connected, the world’s first compound semiconductor cluster. CS Connected,

which is supported by investment from the Welsh and UK governments and the Cardiff Capital Region (CCR),

brings together compound semiconductor material expertise and large-scale semiconductor wafer

manufacturing, combined with academic research, to deliver bespoke solutions to customer using compound

semiconductor materials.

NWF provides volume manufacturing services for the cluster and any customers who have developed their own

products using silicon and compound semiconductors on silicon. It is said to be pivotal to a number of significant

international projects being scrutinised by companies attracted to the one-stop-shop capability of CS

Connected.

http://www.semiconductor-today.com/news_items/2019/jun/nwf-070619.shtml


CS Connected is one of 24 shortlisted projects (and the only one wholly based in Wales) to receive early-stage

funding from the ‘Strength in Places’ Fund of UK Research and Innovation (UKRI) to develop a full-stage business

case submission, benefiting all regions of the UK by enabling them to tap into research and innovation capability

spread across the country, aiming to yield significant economic impact, high-value job creation and regional

growth.

NWF’s CEO Dr Paul James expressed his gratitude to the involved parties for their continuing support that has

strengthened the position of NWF and the wider CS Cluster.

“The Welsh Government has invested significantly in establishing Wales as a global centre for advanced

compound semiconductor technologies and we were pleased to provide support for Newport Wafer Fab so that

they can continue work to attract further commercial investment,” says Ken Skates, the Welsh Government’s

Minister for Economy and Transport. “The cluster and its skilled workforce is hugely important to our economy

and, with world-leading companies and technologies operating and thriving in the region, I look forward to its

continued success and growth in the years ahead,” he adds.

“We are delighted to be supporting a business in growth and one which is helping retain a number of jobs in

South Wales,” comments Warren Lewis, head of corporate banking in South Wales at HSBC UK. “The funding

from HSBC UK is helping NWF grow its customer base both domestically and internationally and, as a result, is

on the path to becoming the largest semiconductor foundry in Europe. We look forward to continuing our

support over the coming years,” he adds.

“The Cardiff Capital Region is committed to creating a complete compound semiconductor eco-system in South-

East Wales to take advantage of the growing prominence of compound semiconductor technologies,” says

Councillor Andrew Morgan, leader of Rhondda Cynon Taf County Borough Council, and chair of the Cardiff

Capital Region’s Regional Cabinet. “We are supporting the establishment of the world’s first compound

semiconductor cluster. In turn, this can place this region at the heart of a sector which is developing technology

which is playing an increasingly vital role in the way we live,” he adds.

“To achieve our aspiration to create the world’s first compound semiconductor cluster, a robust and sustainable

supply chain is critical,” states Councillor Debbie Wilcox, leader of Newport City Council, and a member of the

Cardiff Capital Region’s Regional Cabinet. “This investment will enable support of this, and in the process deliver

the economic and social benefits we aspire to achieve for our local communities here in South-East Wales.”

GlobalFoundries sign long-term agreements for high-volume supply of Soitec’s 300mm SOI wafer SemiconductorToday

GlobalFoundries (GF) of Santa Clara, CA, USA (one of the world’s largest semiconductor foundries, with

operations in Singapore, Germany and the USA) and Soitec of Bernin, near Grenoble, France - which makes

engineered substrates including silicon-on-insulator (SOI) wafers - have signed multiple long-term high-volume

supply agreements for 300mm SOI wafers to meet the growing demand for GF’s differentiated radio-frequency

silicon-on-insulator (RF-SOI), fully depleted silicon-on-insulator (FD-SOI) and silicon photonics technology

platforms. The firms say that the agreements build on the existing close relationship between them to ensure

high-volume manufacturing for years to come.

RF-SOI solutions are used in all smartphones manufactured today and FD-SOI has become the standard

technology for cost-effective, low-power devices in high-volume consumer and Internet of Things (IoT)

applications as well as for mission-critical safety solutions in automotive proximity sensing. Silicon photonics

http://www.semiconductor-today.com/news_items/2019/jun/gf-060619.shtml


technologies enable solutions to support the massive growth in communication infrastructure for data centers

and next-generation 5G communication optical networks.

“GF is delivering and investing in highly differentiated industry-leading technologies required for 5G, IoT, data-

center and automotive applications,” says Bami Bastani, senior VP of business units at GF. “These long-term

agreements with Soitec, a valued partner, represent our commitment to ensure a secure supply of ultra-lower-

power, high-performance SOI solutions and supply that meet customers fast-growing needs and unprecedented

demand in these attractive markets,” he adds.

“GF is leading the industry in providing differentiated SOI solutions, creating more demand for Soitec's

engineered substrates,” comments Soitec’s CEO Paul Boudre. “These agreements reflect the strength of our

long-term partnership as we build the required capacity to meet this growing SOI demand.”

Element Six launches diamond thermal-material-grade Diafilm TM220, offering thermal conductivity over 2200W/mK SemiconductorToday

In booth 1190 at the International Microwave Symposium (IMS 2019) in Boston, MA, USA, Luxembourg-

registered synthetic diamond materials firm Element Six (E6, part of the De Beers Group) is launching the

diamond thermal-material-grade Diafilm TM220, which is claimed to be the first diamond thermal material

engineered to offer industrial users thermal conductivity in excess of 2200W/mK.

The launch is in response to the ever-increasing demand for more content and bandwidth, which is pushing the

boundaries of semiconductor thermal management. The shift to higher frequencies is creating a unique

opportunity for chemical vapor deposition (CVD) diamond, and Element Six says that the launch extends its

portfolio of thermal materials to even higher heat-spreading capabilities.

The new grade of CVD diamond thermal material is suitable for the thermal management of high-power-density

radio frequency (RF) and application-specific integrated circuits (ASIC) devices, as well resistive components for

power management at high frequencies. Diafilm TM220 also has applications in gallium nitride (GaN)-based RF,

in addition to monolithic microwave integrated circuits (MMICs) for phase-array radar, space and satellite, 5G

base stations and beyond. Moreover, the success of terabit rate optoelectronics networks for both metro and

long-haul content delivery is predicated on high-efficiency thermal management.

As with the other material grades of Diafilm TM, TM220 is thermally isotropic, spreading heat with equal

efficiency in a planar direction as well as through the material. Additional Diafilm TM220 properties include

dielectric permittivity, optical clarity, electrical insulation, low density and chemical inertness, making it suitable

for pushing the boundaries of advanced thermal management as either an active or passive component, says

the firm.

“This new material validates the unique multi-functionality of CVD diamond and further demonstrates Element

Six’s leadership and innovation in CVD diamond synthesis and material characterization, where we continue to

open up new areas of advancement,” says Speaking at IMS, Thomas Obeloer, business development manager

for Thermal Applications. “We have already had positive feedback from customers in RF device packaging, x-ray

generation and the high-performance ASIC sector, who were early adopters of the TM220 grade,” he adds.

Material blanks of Diafilm TM220 are available in standard thicknesses and can be made to meet specific

customer requirements. To match the high performance of the diamond, the use of high-quality, sputter-

http://www.semiconductor-today.com/news_items/2019/jun/element-six-030619.shtml


deposited thin-film metallization is offered, and specifications to meet advanced needs for wire bonding or

direct deposition of solder materials onto the CVD diamond can be supplied.

Qorvo cuts June-quarter financial guidance due to US action against Huawei SemiconductorToday

In response to the US Department of Commerce’s Bureau of Industry and Security (BIS) adding Huawei

Technologies Co Ltd and 68 of its affiliates to its ‘Entity List’ prohibiting the sale to Huawei of products covered

by the Export Administration Regulations (EAR) without obtaining an appropriate export license, Qorvo Inc of

Greensboro, NC, USA has updated the financial guidance it provided on 7 May for its fiscal first-quarter 2020 (to

end-June 2019) and full-year 2020.

Sales from its Mobile Products (MP) and Infrastructure and Defense Products (IDP) operating segments to

Huawei and its affiliates accounted for about $469m (15%) of Qorvo’s total revenue in its fiscal full-year 2019

(ended 30 March). Qorvo is continuing to review the impact of the BIS action on its business, including its ability

to apply for and obtain licenses to allow it to ship products to Huawei in the future. Pending further

developments, Qorvo has ceased shipments to Huawei and its affiliates and cannot predict when it will be able

to resume such shipments.

In the meantime, Qorvo is cutting its fiscal first-quarter 2020 guidance for non-GAAP revenue from $780-800m

to $730-750m, for gross margin from 45-45.5%, and for diluted earnings per share from $1.30 to $1.15.

Currently, for fiscal second-quarter 2020, Qorvo’s assumes no sales to Huawei and is projecting revenue to be

roughly flat sequentially. However, due to the ongoing uncertainty of this situation, the firm is not providing any

additional update to its fiscal 2020 guidance at this time.

Cree chosen as silicon carbide partner for Volkswagen’s FAST program SemiconductorToday

Cree Inc of Durham, NC, USA has been selected as the exclusive silicon carbide (SiC) partner for Volkswagen

Group’s ‘Future Automotive Supply Tracks’ initiative (FAST). The aim of FAST is to work together to implement

technical innovations more quickly than before and to realize global vehicle projects more efficiently and

effectively.

“The Volkswagen Group has committed to launch almost 70 new electric models in the next ten years, which is

up from our pledge of 50 and increases the projected number of vehicles to be built on the group’s electric

platforms from 15 million to 22 million in that timeframe,” says Michael Baecker, head of Volkswagen

Purchasing Connectivity. “An effective network is our key to success,” he adds. “Our FAST partners are our

strategic partners, each of them outstanding in their respective field.”

Cree’s CEO Gregg Lowe with Michael Baecker, head of Volkswagen Purchasing Connectivity during Volkswagen

Group’s FAST partner selection ceremony in Wolfsburg, Germany.

Photograph: Cree’s CEO Gregg Lowe with Michael Baecker, head of Volkswagen Purchasing Connectivity during

Volkswagen Group’s FAST partner selection ceremony in Wolfsburg, Germany.

The agreement connects two simultaneous revolutions: the automotive industry’s move from internal

combustion engines to electric vehicles (EVs) and the growing adoption of silicon carbide in the semiconductor

market. It should also drive innovation for both parties.

http://www.semiconductor-today.com/news_items/2019/may/qorvo-210519.shtml

http://www.semiconductor-today.com/news_items/2019/may/cree-vw-140519.shtml


The use of silicon carbide accelerates the automotive industry’s transformation to electric vehicles, enabling

greater system efficiencies that result in electric cars with longer range and faster charging, while reducing cost,

lowering weight and conserving space.

“Cree’s technology is at the heart of the dramatic change underway in EVs, and we are committed to supporting

the automotive industry as it transitions to more efficient, higher-performing SiC-based solutions,” says Cree’s

CEO Gregg Lowe. “VW Group is a global power in the automotive field with a strong commitment to electric

vehicles, and this partnership will leverage the advantages of silicon carbide to enable longer driving distances,

shorter charge times and improved efficiency,” he adds.

Volkswagen Group and Cree will be working with tier-one and power module suppliers to engineer SiC-based

solutions for future Volkswagen Group vehicles. The partnership was announced on 10 May. This follows Cree’s

announcement on 7 May that it is expanding its manufacturing capacity for silicon carbide MOSFETs and wafers.

PowerAmerica Updates WBG Roadmap CompoundSemiconductor

PowerAmerica has unveiled an updated technology roadmap to provide a common vision of the future for the

WBG (wide bandgap) community to work toward.

This roadmap outlines key markets and application areas as well as the performance targets GaN and SiC

technologies are expected to meet over time, technical barriers to achieving those targets, and activities needed

to overcome those barriers.

While WBG technologies such as SiC and GaN offer significant capabilities for power electronics, industry must

overcome numerous challenges including high material and manufacturing costs, reliability perceptions,

packaging and performance requirements, and difficulty coordinating efforts across the entire power electronics

ecosystem.

Recent progress against these challenges in automotive applications, PV inverters, and power supplies is

encouraging; however, SiC and GaN have not taken off as rapidly in traction applications, industrial motor

drives, and wind turbines. Further strides are needed to begin manufacturing these devices at high volumes and

competitive costs across the full range of useful applications.

The following high-level recommendations are a summary of the actions found PowerAmerica's 5- Year

Roadmap Strategy.

Reducing Cost

- Lower the $/ampere of WBG devices and power modules.

- Support vertically integrated fabrication.

- Support and promote early adopter, high-volume WBG applications.

- Establish SiC and GaN open foundries to scale to high-volume manufacturing.

Improving Reliability and Quality

- Establish WBG power electronics reliability at system-level and investigate degradation/failure mechanisms of

devices, modules, or systems.

- Develop open databases for reliability data.

- Develop capability to perform AECQ or JEDEC standard tests for WBG power devices.

-Set dedicated standards for WBG power electronics.

https://compoundsemiconductor.net/article/107297/PowerAmerica_Updates_WBG_Roadmap


Enhancing Performance Capabilities

- Focus on near-term applications to demonstrate the system-level advantages of WBG power devices.

- Support pathways to commercialisation for industry-led projects.

- Promote reference designs, advanced gate drives and modules, and work in advanced peripherals.

Strengthening the Power Electronics Ecosystem

- Continue to offer the Device Bank for quick access to SiC and GaN devices.

- Continue to provide communication mechanisms for different levels of stakeholders, from vendors to end

users.

- Train a WBG power electronics workforce.

- Monitor basic core technologies, state-of-the-art complementary technologies, and long-term applications to

identify promising opportunities.

A more detailed version of the roadmap, available to members only, outlines key markets and application areas

for SiC and GaN power electronics, the performance targets GaN and SiC technologies are expected to meet

over time, technical barriers to achieving those targets, and activities needed to overcome those barriers.


PATENT APPLICATIONS

More than 300 new patent families (inventions) were published in May 2019.

Other patent applicants Anhui East China Photoelectric Technology Research Institute, Beijing University of Technology, Cea - Commissariat à l’Energie Atomique Et Aux Energies Alternatives, Changchun Institute of Optics Fine Mechanics & Physics Chinese Academy of Sciences, China United Northwest Institute For Engineering Design & Research, Dongtai Gaoke Equipment Technology, Fudan University, Fuji Electric, Guangdong Midea Refrigeration Equipment, Infineon Technologies, Infineon Technologies Austria, Institute of Electronic Engineering China Academy of Engineering Physics, Institute of Microelectronics Chinese Academy of Sciences, Intel, Jiangsu Dahang Hongcheng Power Electronics, Lattice Power, Midea, Nanjing University, Nikkiso, Northwestern Polytechnical University, NXP, Panasonic, Sciocs, Shaanxi Reactor Microelectronics, Shanghai Jiao Tong University, Shanghai Xinsheng Semiconductor Technology, Sharp, Shenzhen Original Digital, Sumitomo Chemical, Sun Yat Sen University, University of California, UV Craftory, Wisconsin Alumni Research Foundation, Wuhan University, Xiangneng Hualei Optoelectronic Corppration, Zhangjiagang Ever Power Semiconductor, Advanced Optoelectronic Technology, AGC, Anhui Sanan


Optoelectronics Technology, Anhui University of Technology, Arizona State University, Asahi Kasei, Baoding Zhongchuang Yanyuan Semiconductor Technology, Beijing Ainfo Technology, Beijing Jiaotong University, Beijing Juci Technology, Beijing University of Posts &Telecommunications, BOE Technology, BYD, Chengdu Chenxun Technology, China Cited Core Technology, China Electronics Technology, Chongqing HKC Optoelectronics Technology, Chongqing University, Cornell University, Delta Electronic Enterprise Management, Disco, Elektrotechnicky Ustav SAV, Epistar, Ericsson, ETRA Semiconductor, Ezhou Industrial Technology Research Institute Huazhong University of Science & Technology, Facebook Technologies, Florida International University, Foshan Guoxing Semiconductor Technology, Foshan Huayu Equity Investment Partnership, Fraunhofer, Fujitsu, Fuyang Sineva Material Technology, Gallium Entpr, GaN Systems, General Electric, Global Energy Interconnection Research Institute, Guangdong Institute of Semiconductor Industrial Technology, Guangdong University of Technology, Guangdong Yushi United Holdings, Guangzhou Heguang Tongsheng Technology.

Notable new patent applications

Process for fabrication of an optoelectronic device comprising a plurality of diodes Publication Number: WO2019/092357, FR3073669 Patent Applicant: Cea, Thales The invention relates to a process for fabrication of an optoelectronic device, including: a) adding, to one side of a control circuit (110), a diode stack (150) comprising first and second semiconductor layers (153, 157) of opposite conductivity types, so that the second layer is connected to metal pads (113) of the control circuit; b) forming in the stack trenches bounding a plurality of diodes (176) connected to separate metal pads of the control circuit; c) depositing an insulating layer (178, 178') on the side walls of the trenches; d) partially removing the insulating layer so as to free the flanks of the sections of the first layer that are bounded by the trenches; and e) forming a metallisation (180) coating the side walls and the bottom of the trenches and making contact with the flanks of the sections of the first layer that are bounded by the trenches.

Epitaxial growth and transfer via patterned two-dimensional (2D) layers Publication Number: WO2019/099461 Patent Applicant: MIT

Embodiments including apparatus, systems, and methods for nanofabrication are provided. In one example, a method of manufacturing a semiconductor device includes forming a two-dimensional (2D) layer comprising a 2D material on a first substrate and forming a plurality of holes in the 2D layer to create a patterned 2D layer. The method also includes forming a single-crystalline film on the patterned 2D layer and transferring the single-crystalline film onto a second substrate.

https://sobjprd.questel.fr/sobj/servlet/get_pds/WO201992357A1.pdf?userid=QPRK1002&type=0&pdfid=87932013&ekey=1159



Semiconductor power device Publication Number: US10290730 Patent Applicant: Epistar A semiconductor power device includes an engineered aluminum-nitride substrate structure, and method of fabricating the same are described. The engineered substrate structure is effectively integrated with a transition layer of AlN/AlGaN disposed thereon, a buffer layer disposed on the transition layer having a C—(Al)GaN/u-GaN multiple stacking layered structure, a channel layer, a barrier layer, and an optional SiNx interlayer together, to form a GaN-based semiconductor power device. The GaN buffer layer is capable of achieving sufficient thickness for higher performance. The engineered substrate structure has a core region made of an aluminum nitride (AlN) substrate, a single crystal silicon layer as top material layer thereof, and bonded together with an encapsulated multi-layered structure containing adhesive layers, thin film layers and the AlN substrate. Higher breakdown voltage and improved overall device quality with respect to epitaxy-induced bow, warp, and cracking issues are achieved by the semiconductor power device.

Method for forming a semiconductor structure for a gallium nitride channel device Publication Number: EP3486939, US20190157081, CN109817698 Patent Applicant: IMEC According to an aspect of the present inventive concept there is provided a method of forming a semiconductor structure for a III-N semiconductor channel device, the method comprising: forming a buffer structure on a Si-substrate, wherein forming the buffer structure includes: forming a superlattice including at least one superlattice block , each superlattice block including a repetitive sequence of superlattice units , each superlattice unit including a first layer and a second layer formed on the first layer, wherein the first layer is a carbon-doped Al x Ga 1-x N layer and the second layer is a carbon-doped Al y Ga 1-y N layer, wherein x and y differ from each other and 0‰¤ x‰¤1, 0‰¤y‰¤1, and wherein said at least first and second layers are epitaxially grown at a temperature of 980 °C or lower, and forming a III-N semiconductor channel layer above the buffer structure wherein the channel layer is epitaxially grown at a temperature of 1040 °C or lower and is grown to a thickness of 1 µm or smaller.

https://sobjprd.questel.fr/sobj/servlet/get_pds/US10290730B1.pdf?userid=QPRK1002&type=0&pdfid=87831717&ekey=975

https://sobjprd.questel.fr/sobj/servlet/get_pds/US20190157081A1.pdf?userid=QPRK1002&type=0&pdfid=88073894&ekey=1012


Power and RF devices implemented using an engineered substrate structure Publication Number: WO2019/090212, US20190139859 Patent Applicant: Qromis

An electronic device includes a support structure comprising a polycrystalline ceramic core, a first adhesion layer coupled to the polycrystalline ceramic core, a conductive layer coupled to the first adhesion layer, a second adhesion layer coupled to the conductive layer, and a barrier layer coupled to the second adhesion layer. The electronic device also includes a buffer layer coupled to the support structure, a contact layer coupled to the buffer layer, and a field-effect transistor (FET) coupled to the contact layer.

Stacking-fault-free nonpolar semipolar group III-nitride substrates Publication Number: US20190157068, US20190157069, WO2019/099996, WO2019/100064 Patent Applicant: Saphlux Aspects of the disclosure provide for mechanisms for producing group III-nitride substrates. In accordance with some embodiments, a method for producing a group Ill-nitride substrate is provided. The method may include: forming, on a growth template, an epitaxial layer of a group ID-nitride material comprising a surface with a first crystallographic orientation, wherein the first crystallographic orientation comprises a semipolar orientation or a nonpolar orientation, and separating the epitaxial layer of the group III -nitride material from the growth template to produce the group Ill-nitride substrate, wherein the growth template comprises a semiconductor layer of the group Ill-nitride material. The group III- nitride material may include gallium.

High resolution display device Publication Number: KR10-2019-0052887, EP3483933, US20190140016, CN109768149 Patent Applicant: Samsung Electronics

A display device is provided. The display device includes a substrate, an emission layer configured to emit light, the emission layer including a first semiconductor layer provided on the substrate, an active layer provided on the first semiconductor layer, and a second semiconductor layer provided on the active layer, and a plurality of color converting layers provided on the emission layer and configured to emit light of certain colors from light emitted from the emission layer.





Polarization field assisted heterostructure design for efficient deep ultra-violet light emitting diodes Publication Number: US20190148584, US20190148593 Patent Applicant: Cornell University, University of Notre Dame du Lac A polarization field assisted DUV-LED including a bottom substrate and a n-contact/injection layer formed on the bottom substrate. The n-contact/injection layer includes: a first region for accommodating strain relaxation; a second region for lateral access with a low sheet resistance and higher conductivity compared to the first region to minimize resistive losses and heat generation; and a third region of a graded vertical injection layer with low vertical resistance to minimize heat loss due to vertical resistance. The DUV-LED also includes a p-contact region, and an emitting active region between the n-contact/injection layer and the p-contact region. The injection of electrons and holes into quantum wells (dots, discs) proceeds due to tunneling of electrons and holes under the barriers due to less than 2 nm thickness of barriers. This carrier injection lowers the Turn ON voltage of LEDs and reduces heat generation compared with conventional thermionic over-barrier injection.

Core-shell InGaN/AlGaN quantum nanowire photonic structures Publication Number: US20190148583 Patent Applicant: University of Michigan

A nanowire can include a first semiconductor portion, a second portion including a quantum structure disposed on the first portion, and a second semiconductor portion disposed on the second portion opposite the first portion. The quantum structure can include one or more quantum core structures and a quantum core shell disposed about the one or more quantum core structures. The one or more quantum core structures can include one or more quantum disks, quantum arch-shaped forms, quantum wells, quantum dots within quantum wells or combinations thereof.




Instrinscally tunable and ultra-linear multi-fin MIS HEMT devices Publication Number: WO2019/089727 Patent Applicant: University of California

Devices and methods of the invention use a plurality of Fin structures and or combine a planar portion with Fin structures to compensate for the first derivative of transconductance, gm. In preferred methods and devices, Fins have a plurality of widths and are selected to lead to the separate turn-on voltage thresholds for the largest, intermediate and smallest widths of the MIS HEMT fins to flatten the transconductance gm curve over an operational range of gate source voltage.

LED unit for display and display apparatus having the same Publication Number: US20190165037, WO2019/103568 Patent Applicant: Seoul Viosys

A light emitting device including first, second, and third LED sub-units, and electrode pads disposed on the first LED sub-unit, electrically connected to the LED sub-units, and including a common electrode pad electrically connected to each of the LED sub-units, and first, second, and third electrode pads connected to a respective one of the LED sub-units, in which the common electrode pad, the second electrode pad, and the third electrode pad are electrically connected to the second LED sub-unit and the third LED sub-unit through holes that pass through the first LED sub-unit, the first, second, and third LED sub-units are configured to be independently driven, light generated in the first LED sub-unit emitted to the outside through the second and third LED sub-units, and light generated in the second LED sub-unit is emitted to the outside through the third LED sub-unit.

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