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 Newsletter No. 41 June 2016

III-N Technology

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GANEX | Newsletter No. 41 - III-N Technology 2

METHODOLOGY

Each month

250+ new scientific publications

120+ new patent applications

20+ 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

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TABLE OF CONTENTS (clickable links to chapters)

SCIENTIFIC PUBLICATION ................................................................................................................... 4

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

GROUP 2 - Laser and Coherent Light ....................................................................................................... 8

GROUP 3 - Power Electronics ................................................................................................................. 11

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

GROUP 5 – MEMS and Sensors .............................................................................................................. 18

GROUP 6 - Photovoltaics and Energy harvesting ................................................................................... 20

GROUP 7 - Materials, Technology and Fundamental............................................................................. 21

PRESS RELEASE ................................................................................................................................ 36

PATENT APPLICATION ...................................................................................................................... 46

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SCIENTIFIC PUBLICATION Selection of new scientific articles

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

Information selected by Benjamin Damilano (CRHEA-CNRS)

High-performance InGaN-based green light-emitting diodes with quaternary InAlGaN/GaN superlattice electron blocking layer Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan Optics Express http://dx.doi.org/10.1364/OE.24.011387

In this study, high-performance InGaN-based green light-emitting diodes (LEDs) with a quaternary InAlGaN/GaN superlattice electron blocking layer (QSL-EBL) have been demonstrated. The band structural simulation was employed to investigate the electrostatic field and carriers distribution, show that the efficiency and droop behavior can be intensively improved by using a QSL-EBL in LEDs. The QSL-EBL structure can reduce the polarization-related electrostatic fields in the multiple quantum wells (MQWs), leading to a smoother band diagram and a more uniform carriers distribution among the quantum wells under forward bias. In comparison with green LEDs with conventional bulk-EBL structure, the light output power of LEDs with QSL-EBL was greatly enhanced by 53%. The efficiency droop shows only 30% at 100 A/cm2 comparing to its peak value, suggesting that the QSL-EBL LED is promising for future white lighting with high performance. The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL, United Kingdom J. Appl. Phys. http://dx.doi.org/10.1063/1.4948237

In this paper, we compare and contrast the experimental data and the theoretical predictions of the low temperature optical properties of polar and nonpolar InGaN/GaN quantum well structures. In both types of structure, the optical properties at low temperatures are governed by the effects of carrier localisation. In polar structures, the effect of the in-built electric field leads to electrons being mainly localised at well width fluctuations, whereas holes are localised at regions within the quantum wells, where the random In distribution leads to local minima in potential energy. This leads to a system of independently localised electrons and holes. In nonpolar quantum wells, the nature of the hole localisation is essentially the same as the polar case but the electrons are now coulombically bound to the holes forming localised excitons. These localisation mechanisms are compatible with the large photoluminescence linewidths of the polar and nonpolar quantum wells as well as the different time scales and form of the radiative recombination decay curves. Enhanced photo/electroluminescence properties of Eu-doped GaN through optimization of the growth temperature and Eu related defect environment Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan APL Mater. http://dx.doi.org/10.1063/1.4950826

The influence of growth temperature on the surface morphology and luminescence properties of Eu-doped GaN layers grown by organometallic vapor phase epitaxy was investigated. By using a Eu source that does not contain oxygen in its molecular structure, and varying the growth temperature, the local defect environment around the Eu3+ ions was manipulated, yielding a

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higher emission intensity from the Eu3+ ions and a smoother sample surface. The optimal growth temperature was determined to be 960 °C and was used to fabricate a GaN-based red light-emitting diode with a significantly higher output power. 3D numerical modeling of the carrier transport and radiative efficiency for InGaN/GaN light emitting diodes with V-shaped pits Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, 10617, Taiwan AIP Advances http://dx.doi.org/10.1063/1.4950771

In this paper, influence of a V-pit embedded inside the multiple quantum wells(MQWs)LED was studied. A fully three-dimensional stress-strain solver and Poisson-drift-diffusion solver are employed to study the current path, where the quantum efficiency and turn-on voltage will be discussed. Our results show that the hole current is not only from top into lateral quantum wells (QWs) but flowing through shallow sidewall QWs and then injecting into the deeper lateral QWs in V-pit structures, where the V-pit geometry provides more percolation length for holes to make the distribution uniform along lateral MQWs. The IQE behavior with different V-pit sizes, threading dislocation densities, and current densities were analyzed. Substantially, the variation of the quantum efficiency for different V-pit sizes is due to the trap-assisted nonradiative recombination, effective QW ratio, and ability of hole injections. III-nitride quantum dots for ultra-efficient solid-state lighting Lehigh University, Bethlehem, PA Laser & Photonics Reviews http://dx.doi.org/10.1002/lpor.201500332

III-nitride light-emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs, the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we

present arguments for III-nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD-based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD-based LEDs achieve higher efficiencies at higher currents because of higher spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. If constructed properly, III-nitride light-emitting devices with QD active regions have the potential to outperform quantum well light-emitting devices, and enable an era of ultra-efficient solid-state lighting. Optimisation of GaN LEDs and the reduction of efficiency droop using active machine learning Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK Scientific Reports http://dx.doi.org/10.1038/srep24862

A fundamental challenge in the design of LEDs is to maximise electro-luminescence efficiency at high current densities. We simulate GaN-based LED structures that delay the onset of efficiency droop by spreading carrier concentrations evenly across the active region. Statistical analysis and machine learning effectively guide the selection of the next LED structure to be examined based upon its expected efficiency as well as model uncertainty. This active learning strategy rapidly constructs a model that predicts Poisson-Schrödinger simulations of devices, and that simultaneously produces structures with higher simulated efficiencies. Carrier-induced transient defect mechanism for non-radiative recombination in InGaN light-emitting devices Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, USA Scientific Reports http://dx.doi.org/10.1038/srep24404

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Non-radiative recombination (NRR) of excited carriers poses a serious challenge to optoelectronic device efficiency. Understanding the mechanism is thus crucial to defect physics and technological applications. Here, by using first-principles calculations, we propose a new NRR mechanism, where excited carriers recombine via a Frenkel-pair (FP) defect formation. While in the ground state the FP is high in energy and is unlikely to form, in the electronic excited states its formation is enabled by a strong electron-phonon coupling of the excited carriers. This NRR mechanism is expected to be general for wide-gap semiconductors, rather than being limited to InGaN-based light emitting devices. Degradation and corresponding failure mechanism for GaN-based LEDs Semiconductor lighting Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, No.A35, Qinghua East Road, Haidian District, Beijing P R China AIP Advances http://dx.doi.org/10.1063/1.4953056

The degradation behaviors of high power GaN-based vertical blue LEDs on Si substrates were measured using in-situ accelerated life test. The results show that the dominant failure mechanism would be different during the operation. Besides that, the corresponding associated failure mechanisms were investigated systematically by using different analysis technologies, such as Scan Electron Microscopy, Reflectivity spectroscopy, Transient Thermal Analysis, Raman Spectra, etc. It is shown that initially, the failure modes were mainly originated from the semiconductor die and interconnect, while afterwards, the following serious deterioration of the radiant fluxes was attributed to the package. The interface material and quality, such as die attach and frame, play an important role in determining the thermal performance and reliability. In addition, the heating effect during the operation will also release the compressive strain in the chip. These findings will help to improve the reliability of GaN-based LEDs, especially for the LEDs with vertical structure.

Enhanced light output power of InGaN-based amber LEDs by strain-compensating AlN/AlGaN barriers Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.05.023

We investigated the effect of a combined AlN/Al0.03Ga0.97N barrier on InGaN-based amber light-emitting diodes (LEDs) grown by metalorganic vapor-phase epitaxy. InGaN-based multiple quantum wells with a combined AlN/Al0.03Ga0.97N barrier showed intense photoluminescence with a narrow full-width at half-maximum. The amber LEDs with a combined AlN/Al0.03Ga0.97N barrier achieved a light output power enhanced approximately 2.5-fold at 20 mA compared to that of the LED with a combined AlN/GaN barrier, owing to the reduction of defects in InGaN active layers. Thus, the efficiency of high-In-content InGaN-based LEDs can be improved in the spectrum range of amber. Photoluminescence Decay Dynamics in Blue and Green InGaN LED Structures Revealed by the Frequency-Domain Technique Institute of Applied Research, Vilnius University, Saulėtekio 10, 10222, Vilnius, Lithuania OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055, Regensburg, Germany Journal of Electronic Materials http://dx.doi.org/10.1007/s11664-016-4557-7

An extended study of charge-carrier localization and delocalization in blue and green InGaN light-emitting diode (LED) test structures has been performed. Using the frequency-domain lifetime measurement (FDLM) technique based on direct harmonic modulation of photoluminescence excitation in the frequency range from 1 Hz to 100 MHz, carrier lifetimes were estimated at scales spanning from milliseconds to nanoseconds. The time resolution was determined using fast Fourier transform analysis. A system comprising a radiative and several nonradiative recombination channels was used to describe the complex photoluminescence decay. Due to the broad timescale, even stretched exponential decays

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from 2 ns to 4 ns up to 1.5 μs (stretching parameter 0.5 to 0.6) were revealed. A higher degree of carrier delocalization was observed for the blue compared with the green light-emitting structure, providing qualitative insight into disorder, which is tentatively assigned to spatial fluctuations of the indium concentration in the quantum wells. A nanosecond nonradiative recombination channel for the green light-emitting structure was found to be unsaturated throughout the entire photoexcitation power density range and was interpreted as being related to the higher defect density and lower internal quantum efficiency of the sample. To expand the study of lifetimes to much higher photoexcitation power density, time-resolved photoluminescence kinetics were measured.

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

Information selected by Knowmade

Far-field coupling in nanobeam photonic crystal cavities Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4949359

We optimized the far-field emission pattern of one-dimensional photonic crystal nanobeams by modulating the nanobeam width, forming a sidewall Bragg cross-grating far-field coupler. By setting the period of the cross-grating to twice the photonic crystal period, we showed using three-dimensional finite-difference time-domain simulations that the intensity extracted to the far-field could be improved by more than three orders of magnitude compared to the unmodified ideal cavity geometry. We then experimentally studied the evolution of the quality factor and far-field intensity as a function of cross-grating coupler amplitude. High quality factor (>4000) blue (λ = 455 nm) nanobeam photonic crystals were fabricated out of GaN thin films on silicon incorporating a single InGaN quantum well gain medium. Micro-photoluminescence spectroscopy of sets of twelve identical nanobeams revealed a nine-fold average increase in integrated far-field emission intensity and no change in average quality factor for the optimized structure compared to the unmodulated reference. These results are useful for research environments and future nanophotonic light-emitting applications where vertical in- and out-coupling of light to nanocavities is required. III-nitride quantum dots for ultra-efficient solid-state lighting Lehigh University, Bethlehem, PA Laser & Photonics Reviews http://dx.doi.org/10.1002/lpor.201500332

III-nitride light-emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs,

the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we present arguments for III-nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD-based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD-based LEDs achieve higher efficiencies at higher currents because of higher spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. If constructed properly, III-nitride light-emitting devices with QD active regions have the potential to outperform quantum well light-emitting devices, and enable an era of ultra-efficient solid-state lighting. On the optical and microstrain analysis of graded InGaN/GaN MQWs based on plasma assisted molecular beam epitaxy Photonics Laboratory, Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science & Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Optical Materials Express http://dx.doi.org/10.1364/OME.6.002052

In this paper, c-plane stepped- and graded- InGaN/GaN multiple quantum wells (MQWs) are grown using plasma assisted molecular beam epitaxy (PAMBE) by in situ surface stoichiometry monitoring (i-SSM). Such a technique considerably reduces the strain build-up due to indium clustering within and across graded-MQWs; especially for QW closer to the top which results in mitigation of the quantum-confined Stark effect (QCSE). This is validated by a reduced power dependent photoluminescence blueshift of 10 meV in graded-MQWs as compared to a blueshift of 17 meV for stepped-MQWs. We further analyze

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microstrain within the MQWs, using Raman spectroscopy and geometrical phase analysis (GPA) on high-angle annular dark-field (HAADF)-scanning transmission electron microscope (STEM) images of stepped- and graded-MQWs, highlighting the reduction of ~1% strain in graded-MQWs over stepped-MQWs. Our analysis provides direct evidence of the advantage of graded-MQWs for the commercially viable c-plane light-emitting and laser diodes. New Directions in GaN Photonics Enabled by Electrochemical Processes Yale University ECS Trans. http://dx.doi.org/10.1149/07205.0047ecst

We have developed a novel conductivity based selective electrochemical etching to introduce nanometer sized pores into GaN. The nanoporous (NP) GaN can be considered as a new form of GaN with an unprecedented tunability in optical index. The advantages of NP-GaN for both edge-emitting laser diodes and vertical surface-emitting laser diodes (VCSEL) are subsequently exhibited. Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan Scientific Reports http://dx.doi.org/10.1038/srep26578

Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting

circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and −1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations. InGaN laser diode with metal-free laser ridge using n+-GaN contact layers Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland EXALOS AG, CH-8952 Schlieren, Switzerland Applied Physics Express http://dx.doi.org/10.7567/APEX.9.061004

We report on InGaN edge emitting laser diodes with a top metal electrode located beside the laser ridge. Current spreading over the ridge is achieved via a highly doped n+-type GaN layer deposited on top of the structure. The low sheet resistance of the n+-GaN layer ensures excellent lateral current spreading, while carrier injection is confined all along the ridge thanks to current tunneling at the interface between the n+-GaN top layer and the p++-GaN layer. Continuous-wave lasing at 400 nm with an output power of 100 mW is demonstrated on uncoated facet devices with a threshold current density of 2.4 kAcenterdotcm−2. Shortwave infrared (SWIR) emission from 450 nm InGaN diode lasers Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Str. 2A, Berlin D-12489, Germany Currently with the Paul Drude Institut, Hausvogteiplatz 5-7, 10117 Berlin, Germany OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg, Germany Optical Materials Express http://dx.doi.org/10.1364/OME.6.002139

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hortwave infrared emission from 450 nm InGaN diode lasers is analyzed, and its physical origin is located by SWIR imaging of operating devices. Emission spectra taken in the 900-1700 nm range reveal three main contributions located at 900-1130 nm, 1130-1350 nm, and beyond 1350 nm. In concert with photoluminescence measurements at the substrate, these emission bands are identified as, first, genuine deep-level electroluminescence from the active region and deep-level defect-related emission from the substrate that is pumped by spontaneous 450 nm primary emission, second, pure deep-level defect emission, and third, Planck’s black-body radiation from the entire heated device and an additional deep-level defect contribution.

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

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

Leakage and trapping characteristics in Au-free AlGaN/GaN Schottky barrier diodes fabricated on C-doped buffer layers Department of Electrical Engineering (ESAT), KU Leuven, 3001 Leuven, Belgium IMEC vzw, Kapeldreef 75, , 3001 Leuven, Belgium Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532797

We investigate the DC and dynamic characteristics of AlGaN/GaN Schottky barrier diodes (SBDs) and the diodes with a gated edge termination (GET-SBD) fabricated on unintentional doped (UID) and carbon-doped AlGaN buffers. The off-state characteristics of diodes fabricated on UID buffer are dominated by buffer leakage and buffer breakdown voltage (BV) at higher reverse voltage (inline image larger than 300 V). An improvement in diode leakage and BV can be obtained by fabricating the GET-SBDs on C-doped buffers. A pronounced inline image degradation of the AlGaN/GaN SBDs and GET-SBDs on carbon-doped buffers was observed by dynamic pulsed inline image characterization. This dynamic inline image degradation causes a clear forward current reduction for the AlGaN/GaN GET-SBDs. From combined off-state stress and current transient measurements on AlGaN/GaN SBDs, the collapsed current is recoverable and the inline image degradation is due to a temporary trapping mechanism occurring in the buffer. A distinct trap level of 0.57 eV from trap spectra has been extracted for the diode fabricated on C-doped buffer, and the value was implemented in a TCAD simulator. The simulated results confirm a bulk trapping in the buffer layer for the SBD and show an additional trapping region in the GET-SBD architecture. Investigation of O3-Al2O3/H2O-Al2O3 dielectric bilayer deposited by atomic-layer deposition for GaN MOS capacitors School of Microelectronics, Sun Yat-Sen University, Guangzhou, P.R. China

Institute of Power Electronics and Control Technology, Sun Yat-Sen University, Guangzhou, P.R. China Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532785

In this work, H2O-Al2O3/O3-Al2O3 insulating bilayers were grown on GaN by atomic-layer deposition (ALD) technique using H2O vapor and O3 as oxidants. The electrical and material properties show that the H2O-Al2O3/O3-Al2O3 stack structure appeared to be an appropriate dielectric for GaN MOS devices that had low leakage current densities, high breakdown voltages, and good capacitance–voltage (C–V) curves. The H2O-Al2O3 interlayer between the O3-Al2O3 and GaN efficiently prevented the GaN surface from oxidizing by ozone oxidant by its strong oxidizing power. By taking photo-assisted C–V measurements, it was found that the deep interface state densities at the Al2O3/GaN interface reduced, while increasing the thicknesses of the H2O-Al2O3 interlayer restricted the “Vth shift” phenomenon and improved the stability and reliability of the GaN MOS devices. Ionic liquid gating on atomic layer deposition passivated GaN: Ultra-high electron density induced high drain current and low contact resistance School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4950816

Herein, we report on achieving ultra-high electron density (exceeding 1014 cm−2) in a GaN bulk material device by ionic liquid gating, through the application of atomic layer deposition(ALD) of Al2O3 to passivate the GaNsurface. Output characteristics demonstrate a maximum drain current of 1.47 A/mm, the highest reported among all bulk GaNfield-effect transistors, with an on/off ratio of 105 at room temperature. An ultra-

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high electron density exceeding 1014 cm−2 accumulated at the surface is confirmed via Hall-effect measurement and transfer length measurement. In addition to the ultra-high electron density, we also observe a reduction of the contact resistance due to the narrowing of the Schottky barrier width on the contacts. Taking advantage of the ALDsurface passivation and ionic liquid gating technique, this work provides a route to study the field-effect and carrier transport properties of conventional semiconductors in unprecedented ultra-high charge density regions. Modeling and simulation of bulk gallium nitride power semiconductor devices Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, IL-60616 USA AIP Advances http://dx.doi.org/10.1063/1.4948794

Bulk gallium nitride(GaN) power semiconductor devices are gaining significant interest in recent years, creating the need for technology computer aided design (TCAD) simulation to accurately model and optimize these devices. This paper comprehensively reviews and compares different GaN physical models and model parameters in the literature, and discusses the appropriate selection of these models and parameters for TCAD simulation. 2-D drift-diffusion semi-classical simulation is carried out for 2.6 kV and 3.7 kV bulk GaN vertical PN diodes. The simulated forward current-voltage and reverse breakdown characteristics are in good agreement with the measurement data even over a wide temperature range. A high-efficient driving isolated Drive-by-Microwave half-bridge gate driver for a GaN inverter Green Autonomous Technology Development Center, Automotive & Industrial Systems Company, Panasonic Corporation, Moriguchi, Osaka 570-8501, Japan 2016 IEEE Applied Power Electronics Conference and Exposition (APEC) http://dx.doi.org/10.1109/APEC.2016.7468149

A compact isolated Drive-by-Microwave (DBM) half-bridge gate driver is newly developed, which

can drive GaN-GITs with its constant and low power consumption of 0.9 W even a high switching frequency up to 1.0 MHz due to the gate power time sharing by using the 2.4GHz microwave wireless power transmission. The fabricated GaN isolated DBM half-bridge gate driver provides enough output gate power for GaN-GIT's driving under 140 ??C (Ta). Moreover, the fabricated isolated power source free GaN-GIT inverter module with the isolated DBM half-bridge gate drivers successfully demonstrated a 3-phase motor drive with high power conversion efficiency by covering from its low output. Evaluation of high voltage cascode GaN HEMTs in parallel operation Center for High Performance Power Electronics, The Ohio State University, Columbus, USA 2016 IEEE Applied Power Electronics Conference and Exposition (APEC) http://dx.doi.org/10.1109/APEC.2016.7467991

Paralleling devices is an effective way to achieve higher power applications while still having the convenience brought by discrete devices. However, very few papers investigate the challenges of paralleling Gallium Nitride high electron mobility transistors (GaN HEMTs) in cascode configuration, especially the potential failure modes and its related mechanisms. In this paper, a comprehensive study on paralleled high voltage cascode GaN HEMTs is presented. The influence of paralleling cascode GaN HEMTs on the circuit's stray inductance is studied. Potential operation failure modes and the mechanisms of the cascode GaN HEMTs parallel operation were analyzed in detail. The Ansoft Q3D FEA tool and SPICE-based simulation model were used together to quantify the impacts of the circuit and device mismatch on the paralleled GaN HEMTs operation. The SPICE model is validated by the experimental results Temperature-dependent turn-on loss analysis for GaN HFETs Center for Ultra-wide-area Resilient Electric Energy Transmission Networks (CURENT), Dept. of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, USA

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2016 IEEE Applied Power Electronics Conference and Exposition (APEC) http://dx.doi.org/10.1109/APEC.2016.7467994

Enhancement-mode GaN HFETs enable efficient high-frequency converter design, but this technology is relatively new and exhibits different characteristics from Si or SiC MOSFETs. GaN performance at elevated temperature is especially unique. Turn-on time increases significantly with temperature, and turn-on losses increase as a result. This phenomenon can be explained based on the relationships between junction temperature and GaN device transconductance, and between transconductance and turn-on time. An analytical relationship between temperature and turn-on loss has been derived for the 650-V GS66508 from GaN Systems, and verified with experimental results. Based on this relationship, a detailed model is developed, and a simplified scaling factor is proposed for estimating turn-on loss in e-mode GaN HFETs, using room-temperature switching characterization and typically published datasheet parameters. GaN MIS-HEMT with Low Dynamic ON-Resistance Using SiON Passivation National Chiao Tung University ECS Trans. http://dx.doi.org/10.1149/07205.0019ecst

An effective SiON passivation with high density of positive fixed charges for GaN MIS-HEMTs is demonstrated. The positive fixed charges at the SiON/AlGaN interface effectively reduce the surface potential and expand the quantum well below the Fermi level, thus improving the device performance. The GaN MIS-HEMT with SiON demonstrated a high maximum drain-source current density (IDS,max) of >1 A/mm, a breakdown voltage of 750 V at a drain leakage current of 1 μA/mm, and a well transfer characteristics. The dynamic ON-resistance only increased slightly under a high quiescent bias of 100 V.

Intrinsic Reliability Assessment of 650V Rated AlGaN/GaN Based Power Devices: An Industry Perspective ON Semiconductor ECS Trans. http://dx.doi.org/10.1149/07204.0065ecst

Although astounding performance is already proven by many research papers, the widespread adoption of GaN power devices in the market is still hampered by (1) yield and reproducibility ; (2) cost ; (3) reliability. All three factors are to be considered, but to convince customers to adopt GaN power devices, proven device and product reliability is a must. Cost is kept acceptably low by growing the GaN epi stack on 6 inch and 8inch Si substrates, and by processing the GaN power device technology in standard CMOS production lines. This paper will focus on the most important intrinsic reliability mechanisms for GaN power devices. It will cover gate dielectric reliability, Ohmic contact reliability, accelerated drain stress testing (high temperature reverse bias--HTRB) and high voltage device wear-out testing (high voltage off-state stress--HVOS). Acceleration models are discussed A measurement strategy to extract valuable information about the physical properties of the buffer layers (e.g. activation energies of the traps, conduction mechanisms, …) based on simple transmission line structures, is outlined. Ternary Rare Earth Based Oxides for Nitride Based Devices Forschungszentrum Jülich GmbH ECS Trans. http://dx.doi.org/10.1149/07202.0307ecst

Ternary rare earth oxides are promising candidates for future gate oxides. Therefore GdScO3 and LaLuO3 were investigated with regard to their suitability as gate dielectric. The layers were deposited by pulsed laser deposition and the crystal structure, stoichiometry, layer roughness and band gap were investigated. GdScO3 can be grown hexagonal and amorphous and LaLuO3 can be grown hexagonal, orthorhombic and amorphous. All investigated layers revealed smooth surfaces, exhibited band gaps higher than 5 eV and a permittivity higher

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than 20. These results show that GdScO3 and also LaLuO3 are promising candidates as a future gate dielectric based on nitride semiconductor devices. Electrothermal Performance Optimization of III-Nitride HEMTs Capped with Nanocrystalline Diamond U.S. Naval Research Laboratory ECS Trans. http://dx.doi.org/10.1149/07205.0003ecst

AlGaN/GaN high electron mobility transistors (HEMT) capped with nanocrystalline diamond (NCD) have been demonstrated in the past to outperform electrically and thermally their SiN-passivated counterparts. However, a major process limitation for the integration of a diamond heat spreader has been the O2-plasma damage in the gate opening associated with etching the diamond cap. A sacrificial gate (SG) process for plasma damage-free integration of top-side NCD capping layers is thus developed. On HEMTs with a SG, the addition of a NCD cap did not cause any significant degradation in mobility, carrier density, or sheet resistance. Hall characterization showed minimal (~6%) reduction in sheet carrier density and commensurate increase in sheet resistance, while maintaining mobility and on-state drain current density. Pulsed IDS and on-resistance were improved, indicating that a 10 nm SiN/500 nm NCD could offer improved AlGaN surface passivation compared to a more conventional 100 nm thick PECVD SiN film. Limitations of threshold voltage engineering of AlGaN/GaN heterostructures by dielectric interface charge density and manipulation by oxygen plasma surface treatments GaN Device Technology, RWTH Aachen University, 52074 Aachen, Germany J. Appl. Phys. http://dx.doi.org/10.1063/1.4952382

The interface charge density between the gate dielectric and an AlGaN/GaN heterostructure has a significant impact on the absolute value and stability of the threshold voltage Vth of metal-insulator-semiconductor (MIS) heterostructure

field effect transistor. It is shown that a dry-etching step (as typically necessary for normally off devices engineered by gate-recessing) before the Al2O3 gate dielectric deposition introduces a high positive interface charge density. Its origin is most likely donor-type trap states shifting Vth to large negative values, which is detrimental for normally off devices. We investigate the influence of oxygen plasma annealing techniques of the dry-etched AlGaN/GaN surface by capacitance-voltage measurements and demonstrate that the positive interface charge density can be effectively compensated. Furthermore, only a low Vth hysteresis is observable making this approach suitable for threshold voltage engineering. Analysis of the electrostatics in the investigated MIS structures reveals that the maximum Vth shift to positive voltages achievable is fundamentally limited by the onset of accumulation of holes at the dielectric/barrier interface. In the case of the Al2O3/Al0.26Ga0.74N/GaN material system, this maximum threshold voltage shift is limited to 2.3 V. Low-frequency noise in AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors Center for Nano Materials and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan J. Appl. Phys. http://dx.doi.org/10.1063/1.4952386

Using aluminum titanium oxide (AlTiO, an alloy of Al 2O3 and TiO2) as a high-k gate insulator, we fabricated and investigated AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. From current low-frequency noise (LFN) characterization, we find Lorentzian spectra near the threshold voltage, in addition to 1/f spectra for the well-above-threshold regime. The Lorentzian spectra are attributed to electron trapping/detrapping with two specific time constants, ∼25 ms and ∼3 ms, which are independent of the gate length and the gate voltage, corresponding to two trap level depths of 0.5–0.7 eV with a 0.06 eV difference in the AlTiO insulator. In addition, gate leakage currents are analyzed and attributed to the Poole-

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GANEX | Newsletter No. 41 - III-N Technology 15

Frenkel mechanism due to traps in the AlTiO insulator, where the extracted trap level depth is consistent with the Lorentzian LFN. Vertical architecture for enhancement mode power transistors based on GaN nanowires Institut für Halbleitertechnik, Technische Universität Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany Laboratory for Emerging Nanometrology, Technische Universität Braunschweig, Langer Kamp 6a, D-38106 Braunschweig, Germany Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4952715

The demonstration of vertical GaN wrap-around gated field-effect transistors using GaN nanowires is reported. The nanowires with smooth a-plane sidewalls have hexagonal geometry made by top-down etching. A 7-nanowire transistor exhibits enhancement mode operation with threshold voltage of 1.2 V, on/off current ratio as high as 108, and subthreshold slope as small as 68 mV/dec. Although there is space charge limited current behavior at small source-drain voltages (Vds), the drain current (Id) and transconductance (gm) reach up to 314 mA/mm and 125 mS/mm, respectively, when normalized with hexagonal nanowire circumference. The measured breakdown voltage is around 140 V. This vertical approach provides a way to next-generation GaN-based power devices. Ohmic contacts to Gallium Nitride materials Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 - Zona Industriale, 95121 Catania, Italy Applied Surface Science http://dx.doi.org/10.1016/j.apsusc.2016.04.016

In this review article, a comprehensive study of the mechanisms of Ohmic contact formation on GaN-based materials is presented. After a brief introduction on the physics of Ohmic contacts, a resume of the most important results obtained in literature is reported for each of the systems taken in consideration (n-type GaN, p-type GaN and AlGaN/GaN heterostructures). The optimal metallization schemes and processing conditions

to obtain low resistance Ohmic contacts are presented, discussing the role of the single metals composing the stack and the modification induced by the thermal annealing, either on the metal layers or at the interface with GaN. Physical insights on the mechanism of Ohmic contact formation have been gained by correlating the temperature dependence of the electrical parameters with a morphological/structural analysis of the interface. In the case of the AlGaN/GaN systems, the influence of the heterostructure parameters on the Ohmic contacts has been taken into account adapting the classical thermionic field emission model to the presence of the two dimensional electron gas (2DEG). Finally, the state of the art of “Au-free” metallization to AlGaN/GaN heterostructures is also presented, being this latter a relevant topic for the integration of GaN technology on large scale Silicon devices fabs.

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GANEX | Newsletter No. 41 - III-N Technology 16

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

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

Ionic liquid gating on atomic layer deposition passivated GaN: Ultra-high electron density induced high drain current and low contact resistance School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4950816

Herein, we report on achieving ultra-high electron density (exceeding 1014 cm−2) in a GaN bulk material device by ionic liquid gating, through the application of atomic layer deposition(ALD) of Al2O3 to passivate the GaNsurface. Output characteristics demonstrate a maximum drain current of 1.47 A/mm, the highest reported among all bulk GaNfield-effect transistors, with an on/off ratio of 105 at room temperature. An ultra-high electron density exceeding 1014 cm−2 accumulated at the surface is confirmed via Hall-effect measurement and transfer length measurement. In addition to the ultra-high electron density, we also observe a reduction of the contact resistance due to the narrowing of the Schottky barrier width on the contacts. Taking advantage of the ALDsurface passivation and ionic liquid gating technique, this work provides a route to study the field-effect and carrier transport properties of conventional semiconductors in unprecedented ultra-high charge density regions. Current gain above 10 in sub-10 nm base III-Nitride tunneling hot electron transistors with GaN/AlN emitter Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4949489

We report on a tunnelinghot electron transistor amplifier with common-emitter current gain greater than 10 at a collector current density in excess of 40 kA/cm2. The use of a wide-bandgap

GaN/AlN (111 nm/2.5 nm) emitter was found to greatly improve injection efficiency of the emitter and reduce cold electron leakage. With an ultra-thin (8 nm) base, 93% of the injected hot electrons were collected, enabling a common-emitter current gain up to 14.5. This work improves understanding of the quasi-ballistic hot electron transport and may impact the development of high speed devices based on unipolar hot electron transport. High Efficiency GaN 2.5 to 9 GHz Power Amplifiers Realized in Multilayer LCP Hybrid Technology Skyarna, Halesowen, West Midlands, B63 3TT, U.K. IEEE Microwave and Wireless Components Letters http://dx.doi.org/10.1109/LMWC.2016.2559502

This letter presents wide bandwidth and high efficiency hybrid balanced and push-pull amplifier circuit topologies using Gallium Nitride (GaN) transistors and Liquid Crystal Polymer (LCP) multilayer circuit techniques. Push-pull circuit configurations allow differential and common mode impedances to be presented at even and odd harmonics independently, enabling the continuous mode (class BJ) design space to be exploited. Push-pull amplifiers display drain efficiencies > 40%, output power > 5 W over a bandwidth of 3.5 to 8.5 GHz at 2 dB compression levels, and under CW conditions. By comparison, although designed with identical performance goals, a conventional quadrature balanced amplifier performance is below that of the push-pull configuration. A 0.6–3.8 GHz GaN Power Amplifier Designed Through a Simple Strategy Department of Electronics, Universidad Pedagógica y Tecnológica de Colombia, 150003, Sogamoso, Colombia. IEEE Microwave and Wireless Components Letters http://dx.doi.org/10.1109/LMWC.2016.2549263

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This letter presents the design strategy for an ultra-wideband, high-efficiency hybrid power amplifier based on a commercial GaN-HEMT. The measurement results demonstrate a state-of-the-art fractional bandwidth of 145.5%, with saturated output power higher than 10 W from 0.6 to 3.8 GHz and power added efficiency exceeding 46% in the whole band, thus covering most of the mobile frequencies and making this device suitable for small-base station applications. The simple design approach exploits a N -section transformer, and allows for a priori estimation of the bandwidth: in the proposed case, a good agreement between estimated and measured bandwidth is obtained. Superior transport properties of InGaN channel heterostructure with high channel electron mobility State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, China Applied Physics Express http://dx.doi.org/10.7567/APEX.9.061003

A high-quality AlGaN/InGaN heterostructure is grown by pulsed metal organic chemical vapor deposition on a sapphire substrate. A two-step AlN interlayer is adopted to improve the interface morphology and protect the high-quality InGaN channel. Temperature-dependent Hall measurement shows superior transport properties compared with the traditional GaN channel heterostructure at elevated temperatures. Further, a record highest channel electron mobility of 1681 cm2/(Vcenterdots) at room temperature for an InGaN channel heterostructure is obtained. We attribute the excellent transport properties to the improvement in the material quality, as well as the rationally designed epitaxial structure and well-controlled growth condition. Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China

Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.04.055

Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers are investigated by Hall-effect and current–voltage measurements. It is found that this structure possesses both merits of high two-dimensional electron gas (2DEG) density and low gate leakage current density, while maintaining high 2DEG mobility. Furthermore, temperature dependence of the 2DEG density in this structure is verified to follow a combined tendency of InAlN/GaN (increase) and AlGaN/GaN (decrease) heterostructures with increasing temperature from 90 K to 400 K, which is mainly caused by superposition of the effects from carrier thermal activation induced by extrinsic factors in InAlN layer and the reduced conduction-band discontinuity. Characterization of AlInN/AlN/GaN Heterostructures with Different AlN Buffer Thickness Energy Systems Engineering Department, Kırklareli University, 39000, Kırklareli, Turkey Journal of Electronic Materials http://dx.doi.org/10.1007/s11664-016-4536-z

Two AlInN/AlN/GaN heterostructures with 280-nm- and 400-nm-thick AlN buffer grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and Hall-effect measurements. The symmetric (0002) plane with respect to the asymmetric (101¯1¯2) plane in the 280-nm-thick AlN buffer has a higher crystal quality, as opposed to the 400-nm-thick buffer. The thinner buffer improves the crystallinity of both (0002) and (101¯1¯2) planes in the GaN layers, it also provides a sizeable reduction in dislocation density of GaN. Furthermore, the lower buffer thickness leads to a good quality surface with an rms roughness of 0.30 nm and a dark spot density of 4.0 × 108 cm−2.

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GANEX | Newsletter No. 41 - III-N Technology 18

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

1.02 GHz cross-sectional Lam?? mode resonator with high KT2 exceeding 4.6% Northeastern University, Boston, USA 2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS) http://dx.doi.org/10.1109/MEMSYS.2016.7421712

This paper demonstrates a new class of AlN-based piezoelectric resonators for operation in the microwave frequency range. These novel devices are identified as Cross-Sectional-Lame-Mode resonators (CLMRs) as they rely on the piezoelectric transduction of a Lame mode, in the cross-section of an AlN plate. Such 2-dimensional (2D) mechanical mode of vibration, characterized by motion along both the lateral and the thickness directions, is actuated and sensed piezoelectrically through the coherent combination of the en and en piezoelectric coefficients of AlN. This special feature enables the implementation of CLMRs with high values of electromechanical coupling coefficient (kt2). We demonstrate a kt2 value in excess of 4.6% in a CLMR operating around 1.02 GHz. Such kt2 value is the highest ever reported among AlN resonators employing interdigital-metal-electrodes (IDTs) to actuate and to sense the mechanical motion. High-Speed and Low-Energy Nitride Memristors Hewlett Packard LabsPalo Alto, CA 94304, USA Department of Materials Science and EngineeringSeoul National University of Science and TechnologySeoul 01811, South Korea Advanced Functional Materials http://dx.doi.org/10.1002/adfm.201600680

High-performance memristors based on AlN films have been demonstrated, which exhibit ultrafast ON/OFF switching times (≈85 ps for microdevices with waveguide) and relatively low switching current (≈15 μA for 50 nm devices). Physical characterizations are carried out to understand the device switching mechanism, and rationalize speed and energy performance. The formation of

an Al-rich conduction channel through the AlN layer is revealed. The motion of positively charged nitrogen vacancies is likely responsible for the observed switching. Improved GaN Based Hydrogen Sensors Hongik University ECS Trans. http://dx.doi.org/10.1149/07205.0023ecst

To improve the conventional GaN based hydrogen sensor devices, catalytically active Pt nanonetworks were applied to active gate area of AlGaN/GaN HEMT, and surface roughening of active area in nonpoalar a-plane and semipolar GaN diode by using Photo-electrochemical etching was employed. When the active gate region of an AlGaN/GaN sensor is functionalized with platinum nanostructures that contain a larger surface area offering more active sites for hydrogen molecules to be adsorbed, the drain current response was dramatically improved. Also, the extended rough surface of the diodes showed improved hydrogen detection sensitivity due to the presence of more available adsorption sites, resulting in effective variations of the Schottky barrier height. Methods for precisely controlling the residual stress and temperature coefficient of the frequency of a MEMS resonator based on an AlN cavity silicon-on-insulator platform Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way #08-02 Tower A (Innovis), 138634, Singapore Exploit Technologies Pte Ltd, A*STAR, 30 Biopolis Street, #09-02 Matrix, 138671, Singapore Journal of Micromechanics and Microengineering http://dx.doi.org/10.1088/0960-1317/26/7/074003

In this paper, we report an experimentally verified numerical model developed for precisely predicting and controlling the initial bending of a multi-layer-stack composite cantilever structure which is caused by the residual stress of the

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individual constituting layers, as well as the cantilever's thermal coefficient of frequency (TCF). The developed model is exemplified using a flexural-mode cantilever resonator according to the process flow of the aluminium nitride (AlN) cavity silicon-on-insulator (SOI) platform. The same AlN cavity SOI platform is also utilized to fabricate the exemplified cantilever, which is then used to experimentally verify the accuracy and consistency of the numerical model. The experimental results show a difference of less than 3.5% is observed in terms of the deflection at the tip of the cantilever as compared with the numerical model, demonstrating the accuracy of the developed numerical model and the feasibility to optimize the cantilever's initial deflection and TCF simultaneously, achieving minimum values for both parameters at the same time. VHF-band biconvex AlN-on-silicon micromechanical resonators with enhanced quality factor and suppressed spurious modes Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong Journal of Micromechanics and Microengineering http://dx.doi.org/10.1088/0960-1317/26/6/065012

This paper reports experimental results demonstrating the use of biconvex-edge designs to enhance the quality factor (Q) in aluminum nitride (AlN)-on-silicon micromechanical resonators. The proposed biconvex design serves to confine the acoustic energy to the center of the resonators, thus reducing out-of-plane bending on the supporting tethers that contribute to acoustic energy leakage, thereby enhancing Q. We here demonstrate that the biconvex design concept can be scaled and applied across a range of operating frequencies from 70 to 141 MHz with the notable effect of boosting Q relative to conventional flat-edge designs. Our measurements of several resonators have shown that the biconvex designs result in an increase in Q by 4–10 times compared to conventional flat-edge designs. In addition, we have also investigated the effect of using different lengths of supporting tethers on Q for both biconvex and flat-edge designs. From the measurement results of devices under test, we have found that the

variation in Q as a function of tether length was insignificant compared to the increase in Q going from a flat-edge to biconvex design. As such, the level of enhancement for Q using the biconvex design is much more significant compared to varying the geometry of the support structures. Interestingly, the biconvex shape causes a modal split that gives rise to an additional anti-symmetric mode not found in the flat-edge design. We show experimentally that this spurious anti-symmetric mode can be suppressed by over 54 dB by applying a novel center-loaded electrode design that matches the strain field pattern of the desired symmetric mode. Close agreements between the 3D coupled-domain finite element simulations and the measured results of fabricated devices have been obtained for the resonant frequencies and motional capacitances. A Bamboo-Like GaN Microwire-Based Piezotronic Memristor Department of Physics and Laboratoryof Materials Physic, Zhengzhou University, Zhengzhou, P. R. China Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, National Center for Nanoscience and Technology (NCNST), Beijing, P. R. China Advanced Functional Materials http://dx.doi.org/10.1002/adfm.201600962

Bamboo-like gallium nitride (GaN) microwires are synthesized via chemical vapor deposition (CVD) to fabricate piezotronic memristors. Defect boundary areas (DBAs) near the bamboo knots produce apparent switching between high and low resistance states upon sweeping of the magnitudes of the biased voltages across the GaN microwire-based devices at room temperature. Furthermore, by coupling the piezoelectric and semiconducting properties in the GaN microwire, the piezotronic effect is introduced to effectively modulate the SET voltages via strain-induced piezoelectric polarizations created at the DBA interface upon mechanical deformation. The experimental results indicate that the device remembered the most recent resistance states when the power is turned off, and the waveform is tunable because of the delayed switching effect.

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GANEX | Newsletter No. 41 - III-N Technology 20

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

Information selected by Knowmade

A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane Department of Electrical and Computer Engineering, McGill University, Montreal, Canada Chemistry - A European Journal http://dx.doi.org/10.1002/chem.201601642

A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e− photoreduction to CH4 at −1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e− reduced CO (ca. 0.6 %). Enhanced InGaN/GaN photoelectrodes for visible-light-driven hydrogen generation by surface roughening Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, P. R. China National Laboratory of Solid Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, P. R. China Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532545

III-Nitride semiconductor materials are considered as promising candidates for photoelectrodes (PEs) due to their adjustable direct band gap covering a very broad spectral range. In this study, InGaN/GaN based p–i–n photoelectrodes have been fabricated and nano-sized surface roughening process has been applied. The photocurrent gets 2.5 times enhancement and the incident photon conversion efficiency (IPCE) is

improved to be ∼30% at the wavelength of 400 nm. In addition, the turn-on voltages of InGaN/GaN-based PEs have been effectively reduced from +0.8 V down to about −0.4 V (vs. reversible hydrogen potential, RHE). Such improvements are mainly attributed to reduced dislocation density, increased surface area, and optimized build-in electrical field. These findings give innovative insight to improve photoelectrochemical devices for hydrogen generation. Wafer-scale porous GaN single crystal substrates and its application in energy storage Key Laboratory of Processing and Testing Technology of Glass & Functional Ceramics of Shandong Province, School of Materials Science and Engineering, Qilu University of Technology, Jinan 250353, PR China CrystEngComm http://dx.doi.org/10.1039/C6CE00741D

The porous GaN has recently attracted much interest due to its high surface area, shift of bandgap and efficient luminescence. However, the porous GaN obtained so far are mainly fabricate by electrochemical etching or photoelectrochemical etching method. Here, we report the fabrication of wafer-scale (2inch) porous GaN by a novel and simple high temperature annealing process. A model is proposed, based on scanning electron microscopy as well as stabilities of GaN crystallographic plane to explain the formation mechanism of the porous GaN. Improvement crystal quality, enhancement optical quality and strain relaxation of porous GaN are confirmed by HRXRD, PL and Raman results. A three-electrode system based on the porous GaN electrodes is assembled. The good capacitive behavior and superior electrochemical reversibility validates the concept of porous GaN based supercapacitors and points to potentials in energy storage applications.

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GANEX | Newsletter No. 41 - III-N Technology 21

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

NANO

Information selected by Jesús Zúñiga Pérez (CRHEA-CNRS)

Shape dependent electronic properties of wurzite GaN nanowire Nanomaterials Research Group, ABV-Indian Institute of Information Technology and Management (IIITM), Gwalior-474015, India AIP Conf. Proc. http://dx.doi.org/10.1063/1.4946122

In the present work, energetic stability and electronic behavior of triangular and square shaped wurzite GaN NW oriented along [1100] and [11 2 0] direction has been investigated by employing ab-initio DFT calculation. Structural analysis suggests that triangular shaped NW undergoes strong surface reconstruction compared to square shaped NW. However, binding energy reveals that square shaped NW is energetically more feasible than triangular NW. Further, from electronic band structure we observe that both structures are metallic with higher metallicity for triangular shaped NW. Composition analysis of coaxially grown InGaN multi quantum wells using scanning transmission electron microscopy Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee NW1, 28359 Bremen, Germany J. Appl. Phys. http://dx.doi.org/10.1063/1.4948385

GaNnanotubes with coaxial InGaNquantum wells were analyzed by scanning transmission electron microscopy in order to determine their structural properties as well as the indium distribution across the InGaNquantum wells. For the latter, two process steps are necessary. First, a technique to prepare cross-sectional slices out of the nanotubes has been developed. Second, an existing scanning transmission electron microscopy analysis technique has been extended with respect to the special crystallographic

orientation of this type of specimen. In particular, the shape of the nanotubes, their defect structure, and the incorporation of indium on different facets were investigated. The quantum wells preferentially grow on m-planes of the dodecagonally shaped nanotubes and on semipolar top facets while no significant indium signal was found on a-planes. An averaged indium concentration of 6% to 7% was found by scanning transmission electron microscopy analysis and could be confirmed by cathodoluminescence measurements. Temperature dependent growth of GaN nanowires using CVD technique Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India AIP Conf. Proc. http://dx.doi.org/10.1063/1.4947682

Growth of GaN nanowires have been carried out on sapphire substrates with Au as a catalyst using chemical vapour deposition technique. GaN nanowires growth have been studied with the experimental parameter as growth temperature. Diameter of grown GaN nanowires are in the range of 50 nm to 100 nm while the nanowire length depends on growth temperature. Morphology of the GaN nanowires have been studied by scanning electron microscopy. Crystalline nature has been observed by XRD patterns. Optical properties of grown GaN nanowires have been investigated by photoluminescence spectra. Molecular beam epitaxy of single crystalline GaN nanowires on a flexible Ti foil Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin, Germany Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4950707

We demonstrate the self-assembledgrowth of vertically aligned GaNnanowire ensembles on a flexible Ti foil by plasma-assisted molecular beam

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epitaxy. The analysis of single nanowires by transmission electron microscopy reveals that they are single crystalline. Low-temperature photoluminescence spectroscopy demonstrates that in comparison to standard GaNnanowiresgrown on Si, the nanowires prepared on the Ti foil exhibit an equivalent crystalline perfection, a higher density of basal-plane stacking faults, but a reduced density of inversion domain boundaries. The room-temperature photoluminescence spectrum of the nanowire ensemble is not influenced or degraded by the bending of the substrate. The present results pave the way for the fabrication of flexible optoelectronic devices based on GaNnanowires on metal foils. Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal–Organic Vapor Phase Epitaxy Institut für Nanoarchitekturen für die Energieumwandlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner Platz 1, 14109 Berlin, Germany Institute of Optics, Information and Photonics, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Staudtstr. 7/B2, 91058 Erlangen, Germany Max Planck Institute for the Science of Light, Günther-Scharowsky-Str. 1, 91058 Erlangen, Germany Nano Lett. http://dx.doi.org/10.1021/acs.nanolett.5b03889

Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal–organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor–liquid–solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy,

spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells. Nucleation, Growth, and Bundling of GaN Nanowires in Molecular Beam Epitaxy: Disentangling the Origin of Nanowire Coalescence Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5−7, 10117 Berlin, Germany Nano Lett. http://dx.doi.org/10.1021/acs.nanolett.6b01044

We investigate the nucleation, growth, and coalescence of spontaneously formed GaN nanowires in molecular beam epitaxy combining the statistical analysis of scanning electron micrographs with Monte Carlo growth models. We find that (i) the nanowire density is limited by the shadowing of the substrate from the impinging fluxes by already existing nanowires, (ii) shortly after the nucleation stage, nanowire radial growth becomes negligible, and (iii) coalescence is caused by bundling of nanowires. The latter phenomenon is driven by the gain of surface energy at the expense of the elastic energy of bending and becomes energetically favorable once the nanowires exceed a certain critical length. Vertically Oriented Growth of GaN Nanorods on Si Using Graphene as an Atomically Thin Buffer Layer Max Planck Institute for the Science of Light, Günther-Scharowsky-Str. 1, D-91058 Erlangen, Germany Nano Lett. http://dx.doi.org/10.1021/acs.nanolett.6b00484

The monolithic integration of wurtzite GaN on Si via metal–organic vapor phase epitaxy is strongly hampered by lattice and thermal mismatch as well as meltback etching. This study presents single-

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layer graphene as an atomically thin buffer layer for c-axis-oriented growth of vertically aligned GaN nanorods mediated by nanometer-sized AlGaN nucleation islands. Nanostructures of similar morphology are demonstrated on graphene-covered Si(111) as well as Si(100). High crystal and optical quality of the nanorods are evidenced through scanning transmission electron microscopy, micro-Raman, and cathodoluminescence measurements supported by finite-difference time-domain simulations. Current–voltage characteristics revealed high vertical conduction of the as-grown GaN nanorods through the Si substrates. These findings are substantial to advance the integration of GaN-based devices on any substrates of choice that sustains the GaN growth temperatures, thereby permitting novel designs of GaN-based heterojunction device concepts. Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan Scientific Reports http://dx.doi.org/10.1038/srep26578

Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular

polarizations of the left- and right-hand chiral lasers were 1.4 and −1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations. Vertical architecture for enhancement mode power transistors based on GaN nanowires Institut für Halbleitertechnik, Technische Universität Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany Laboratory for Emerging Nanometrology, Technische Universität Braunschweig, Langer Kamp 6a, D-38106 Braunschweig, Germany Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4952715

The demonstration of vertical GaN wrap-around gated field-effect transistors using GaN nanowires is reported. The nanowires with smooth a-plane sidewalls have hexagonal geometry made by top-down etching. A 7-nanowire transistor exhibits enhancement mode operation with threshold voltage of 1.2 V, on/off current ratio as high as 108, and subthreshold slope as small as 68 mV/dec. Although there is space charge limited current behavior at small source-drain voltages (Vds), the drain current (Id) and transconductance (gm) reach up to 314 mA/mm and 125 mS/mm, respectively, when normalized with hexagonal nanowire circumference. The measured breakdown voltage is around 140 V. This vertical approach provides a way to next-generation GaN-based power devices. Controlled morphology of regular GaN microrod arrays by selective area growth with HVPE Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya, Aichi 464-8603, Japan Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Aichi 464-8603, Japan Venture Business Laboratory (VBL), Nagoya University, Nagoya, Aichi 464-8603, Japan Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.05.008

The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire

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GANEX | Newsletter No. 41 - III-N Technology 24

templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H2/N2 carrier gas ratio, growth temperature, and absolute NH3/HCl gas flow resulted in changes in the growth morphology. In particular, for an optimized mixed-carrier gas ratio of H2 to N2, we achieved vertically well-aligned microrods. The topmost regions of the GaN microrods were terminated with pyramidal facets, indicating typical Ga polarity. The optical properties of the grown microrods were characterized by cathodoluminescence (CL) at a low temperature. This revealed that the GaN microrods had high crystal quality since they exhibited suppressed yellow luminescence as well as strong band edge emission.

NON/SEMI POLAR Information selected by

Philippe De Mierry (CRHEA-CNRS) Structure and composition of non-polar (11-20) InGaN nanorings grown by modified droplet epitaxy Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201670530

Nitride-based quantum dots (QDs) show promise as sources for single photon emission, enabling comparably high temperature emission and access to the blue and green spectral region. Some droplets forming during modified droplet epitaxy on non-polar (11-20) surfaces of InGaN epilayers on GaN are associated with underlying ring-like structures. The work by Springbett et al. (pp. 840–844) discusses droplet etching as a possible mechanism for ring formation, whereby In and Ga atoms are incorporated into the droplet and diffuse to the edges. Thereafter, recrystallization occurs, leading to the formation of a ring. It is hypothesised that the droplet then creeps in a direction determined by the crystallographic anisotropy and the surface energetics. Once this movement halts, etching continues. The resulting structure consists of a recession enclosed by a double ring. Transmission

electron microscopy (TEM) analysis shows the droplets move along the ⟨0001⟩ c-axis, and energy dispersive X-ray spectroscopy (EDXS) indicates that they have a very high In content. These studies may help reveal the underlying QD formation mechanism during modified droplet epitaxy. Toward defect-free semi-polar GaN templates on pre-structured sapphire Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201670532

There is a need for large-size, cost-effective and high-quality semi-polar GaN templates for the development of semi-polar GaN based light emitting diodes (LEDs), which are promising to give an increased light emitting efficiency. As one of the approaches, semi-polar templates have been successfully developed on pre-structured sapphire (patterned) substrates. This a pproach involves an initial growth of GaN along the c-direction followed by a coalescence between adjacent GaN stripes to form a continuous semi-polar surface. Using transmission electron microscopy (TEM), Yisong Han et al. (pp. 834–839) provide a detailed microstructural characterisation of semi-polar (11-22) GaN layers grown by MOVPE on pre-structured r-plane sapphire. They focus on the study of the generation and propagation of defects as the growth progresses, and the impact of incorporating a SiN interlayer for dislocation reduction before coalescence and its microstructure on different facets. In addition, a series of Si-doped marker layers were deposited at different stages of the growth, which provide important insight into the evolution of the GaN stripes before coalescence as a function of growth temperature.

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GANEX | Newsletter No. 41 - III-N Technology 25

The microstructure of non-polar a-plane (112¯2¯0) InGaN quantum wells Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom J. Appl. Phys. http://dx.doi.org/10.1063/1.4948299

Atom probe tomography and quantitative scanning transmission electron microscopy are used to assess the composition of non-polar a-plane (11-20) InGaN quantum wells for applications in optoelectronics. The average quantum well composition measured by atom probe tomography and quantitative scanning transmission electron microscopy quantitatively agrees with measurements by X-ray diffraction. Atom probe tomography is further applied to study the distribution of indium atoms in non-polar a-plane (11-20) InGaN quantum wells. An inhomogeneous indium distribution is observed by frequency distribution analysis of the atom probe tomography measurements. The optical properties of non-polar (11-20) InGaN quantum wells with indium compositions varying from 7.9% to 20.6% are studied. In contrast to non-polar m-plane (1-100) InGaN quantum wells, the non-polar a-plane (11-20) InGaN quantum wells emit at longer emission wavelengths at the equivalent indium composition. The non-polar a-plane (11-20) quantum wells also show broader spectral linewidths. The longer emission wavelengths and broader spectral linewidths may be related to the observed inhomogeneous indium distribution. Terahertz intersubband photodetectors based on semi-polar GaN/AlGaN heterostructures Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary's Street, Boston, Massachusetts 02215, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4950852

Terahertz intersubband photodetectors are developed based on GaN/AlGaN quantum wellsgrown on a free-standing semi-polar (202¯1¯)(202¯1¯)GaN substrate. These quantum wells are nearly free of the polarization-induced internal electric fields that severely complicate the

design of nitride intersubband devices on traditional c-plane substrates. As a result, a promising bound-to-quasi-bound THz photodetector design can be implemented. Pronounced photocurrent peaks at the design frequency near 10 THz are measured, covering frequencies that are fundamentally inaccessible to existing arsenide intersubband devices due to reststrahlen absorption. This materials system provides a favorable platform to utilize the intrinsic advantages of nitride semiconductors for THz optoelectronics. Infrared absorption of hydrogen-related defects in ammonothermal GaN Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4952388

Polarization controlled Fourier transform infrared (FTIR) absorption measurements were performed on a high quality m-plane ammonothermal GaN crystal grown using basic chemistry. The polarization dependence of characteristic absorption peaks of hydrogen-related defects at 3000–3500 cm−1 was used to identify and determine the bond orientation of hydrogenated defect complexes in the GaN lattice. Majority of hydrogen was found to be bonded in gallium vacancy complexes decorated with one to three hydrogen atoms (VGa-H1,2,3) but also hydrogenated oxygen defect complexes, hydrogen in bond-center sites, and lattice direction independent absorption were observed. Absorption peak intensity was used to determine a total hydrogenated VGa density of approximately 4 × 1018 cm−3, with main contribution from VGa-H1,2. Also, a significant concentration of electrically passive VGa-H3 was detected. The high density of hydrogenated defects is expected to have a strong effect on the structural, optical, and electrical properties of ammonothermal GaN crystals.

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GANEX | Newsletter No. 41 - III-N Technology 26

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL, United Kingdom J. Appl. Phys. http://dx.doi.org/10.1063/1.4948237

In this paper, we compare and contrast the experimental data and the theoretical predictions of the low temperature optical properties of polar and nonpolar InGaN/GaN quantum well structures. In both types of structure, the optical properties at low temperatures are governed by the effects of carrier localisation. In polar structures, the effect of the in-built electric field leads to electrons being mainly localised at well width fluctuations, whereas holes are localised at regions within the quantum wells, where the random In distribution leads to local minima in potential energy. This leads to a system of independently localised electrons and holes. In nonpolar quantum wells, the nature of the hole localisation is essentially the same as the polar case but the electrons are now coulombically bound to the holes forming localised excitons. These localisation mechanisms are compatible with the large photoluminescence linewidths of the polar and nonpolar quantum wells as well as the different time scales and form of the radiative recombination decay curves. Stacking fault emission in GaN: Influence of n-type doping Institute of Quantum Matter/Semiconductor Physics Group, University of Ulm, Albert-Einstein-Allee 45, 89069 Ulm, Germany J. Appl. Phys. http://dx.doi.org/10.1063/1.4949512

We present spatially and spectrally resolved cathodoluminescence investigations on the cross section of semipolar (112¯2)(112¯2)gallium nitride epitaxial layers with high background doping level. The locally varying high carrier concentration leads in emission to a free electron recombination band (FERB) governed on the high energy side by conduction band filling. For the basal plane stacking fault (BSF) of type I1, typically emitting at

≈3.41 eV in low dopedGaN, we find a blue shift in emission correlated to the FERB high energy tail. This shift can be perfectly modeled and understood in a quantum well model for the BSF, taking also into account the varying doping level in the barrier region. Thus, the carrier concentration can be finally calculated either from the actual position of the I1 BSF or alternatively from the FERB-related near band edge emission. Strain relaxation in semipolar (202¯1)(202¯1) InGaN grown by plasma assisted molecular beam epitaxy Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw, Poland J. Appl. Phys. http://dx.doi.org/10.1063/1.4948963

Strain relaxation in semipolar (202¯1)(202¯1)InGaN layers grown by plasma assisted molecular beam epitaxy(PAMBE) was investigated with high-resolution X-ray diffraction(XRD) reciprocal space mapping, cathodoluminescence (CL), fluorescent light microscopy (FLM), and atomic force microscopy. We find that XRD detects lattice relaxation much later than its actual onset occurs. Other techniques used in this study allowed to detect local footprints of plastic relaxation before it was evidenced by XRD: at the initial stages of strain relaxation, we observed changes in layer morphology, i.e., formation of short trench line segments on the surface along the ⟨112¯0112¯0⟩ direction as well as dark lines in CL and FLM. The misfit dislocations formation and glide were observed in two slip systems: initially in basal slip system ⟨112¯0⟩{0001}112¯0⟩{0001} and for larger amount of strain in non-basal, prismatic slip system⟨112¯0⟩{11¯00}⟨112¯0⟩{11¯00}. Experimentally determined critical thickness for InGaN layers grown by PAMBE on semipolar (202¯1)(202¯1) bulk GaN substrates agrees well with literature data obtained with metalorganic vapor phase epitaxy and follows the Matthews-Blakeslee model prediction. We discuss the impact of substrate structural properties on the strain relaxation onset and mechanisms. We also

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GANEX | Newsletter No. 41 - III-N Technology 27

describe the layer morphology and surface roughness evolution related to the increasing In content and strain relaxation of the semipolar (202¯1)(202¯1)InGaN layers. Crystal orientation dependent intersubband transition in semipolar AlGaN/GaN single quantum well for optoelectronic applications School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, USA J. Appl. Phys. http://dx.doi.org/10.1063/1.4948667

The optical properties of intersubband transition in a semipolar AlGaN/GaN single quantum well(SQW) are theoretically studied, and the results are compared with polar c-plane and nonpolar m-plane structures. The intersubband transition frequency, dipole matrix elements, and absorption spectra are calculated for SQW on different semipolar planes. It is found that SQW on a certain group of semipolar planes (55° < θ < 90° tilted from c-plane) exhibits low transition frequency and long wavelength response with high absorption quantum efficiency, which is attributed to the weak polarization-related effects. Furthermore, these semipolar SQWs show tunable transition frequency and absorption wavelength with different quantum well thicknesses, and stable device performance can be achieved with changing barrier thickness and Al compositions. All the results indicate that the semipolar AlGaN/GaN quantum wells are promising candidate for the design and fabrication of high performance low frequency and long wavelength optoelectronic devices. Formation and characteristics of AlGaN-based three-dimensional hexagonal nanopyramid semi-polar multiple quantum wells Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China Beijing Engineering Research Center for the 3rd Generation Semiconductor Materials and Application, Beijing 100083, China Nanoscale http://dx.doi.org/10.1039/C5NR09056C

We demonstrated for the first time the formation and study of semi-polar AlGaN multiple-quantum-wells (MQWs) grown on highly regular hexagonal AlN nanopyramids. The AlN nanopyramids were obtained by a metal–organic chemical vapor phase deposition regrowth method on a well-ordered AlN nanorod array prepared by a top-down etching process. The growth mechanism of the AlN nanopyramids was ascribed to the slow growth of the (10[1 with combining macron]1) semi-polar plane, which resulted from hydrogen passivation. Beneath the semi-polar facets, air voids were formed. This was attributed to the insufficient delivery of gas reactants to the bottom of the nanorods during the growth process. The polarization effect in semi-polar AlGaN MQWs was numerically calculated. The results showed that the internal electric field (IEF) in the semi-polar MQWs was remarkably reduced by 80% in comparison with c-plane MQWs. Power dependent photoluminescence indicated that the semi-polar AlGaN MQWs had negligible wavelength shifts that resulted from the reduced IEF, which was in accordance with theoretical predictions. In addition, epitaxial strain was greatly relieved in the AlN regrowth layer, which was revealed from the peak shift of the E2(high) phonon using micro-Raman spectroscopy. The advantages of AlGaN-based hexagonal nanopyramid semi-polar three dimensional nanostructures would lead to a large improvement of output power in UV-LEDs. Nucleation and growth of (1011) semi-polar AlN on (0001) AlN by Hydride Vapor Phase Epitaxy Platform for Characterization and Test, Suzhou Institute of Nano-tech and Nano-bionics, CAS, Suzhou, 215123, China Scientific Reports http://dx.doi.org/10.1038/srep26040

Wurtzite AlN is widely used for deep ultraviolet optoelectronic devices (DUV), which are generally grown along the [0001]-direction of the wurtzite structure on currently available substrates. However, huge internal electrostatic fields are presented within the material along [0001] axis induced by piezoelectric and spontaneous polarization, which has limited the internal

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GANEX | Newsletter No. 41 - III-N Technology 28

quantum efficiency of AlN based DUV LEDs dramatically. The internal fields can be strongly reduced by changing the epitaxial growth direction from the conventional polar c-direction into less polar crystal directions. Twinned crystal is a crystal consisting of two or more domains with the same crystal lattice and composition but different crystal orientations. In other words, twins can be induced to change crystal directions. In this work we demonstrated that the epitaxial growth of () semi-polar AlN on (0001) AlN by constructing () and () twin structures. This new method is relative feasible than conventional methods and it has huge prospect to develop high-quality semi-polar AlN. High-brightness semipolar (𝟤𝟢-2-1) blue InGaN/GaN superluminescent diodes for droop-free solid-state lighting and visible-light communications Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 21534, Saudi Arabia Optics Letters http://dx.doi.org/10.1364/OL.41.002608

A high-brightness, droop-free, and speckle-free InGaN/GaN quantum well blue superluminescent diode (SLD) was demonstrated on a semipolar (20-2-1) GaN substrate. The 447-nm emitting SLD has a broad spectral linewidth of 6.3 nm at an optical power of 123 mW. A peak optical power of 256 mW was achieved at 700 mA CW injection current. By combining YAG:Ce phosphor, SLD-generated white light shows a color-rendering index (CRI) of 68.9 and a correlated color temperature (CCT) of 4340 K. The measured frequency response of the SLD revealed a −3  dB bandwidth of 560 MHz, thus demonstrating the feasibility of the device for both solid-state lighting (SSL) and visible-light communication (VLC) applications.

OTHER (fundamental, material, characterization, equipment)

Information selected by Agnès Trassoudaine (Université d'Auvergne)

and Yvon Cordier (CRHEA-CNRS)

Investigation of low-temperature cathodoluminescence mechanism of Er-doped GaN thick films by ion implantation Department of Physics, Suzhou University of Science and Technology, Suzhou China Chinese Optics Letters https://www.osapublishing.org/col/abstract.cfm?URI=col-14-5-051602

Er ions are implanted into the GaN thick films grown by hydride vapor phase epitaxy. The implantation energy is 200 keV and the implantation doses are 1×1013, 1×1014, 1×1015, and 5×1015  atom/cm2, respectively. The effects of the implantation dose and annealing temperature on the GaN band-edge luminescence are investigated. The cathodoluminescence spectra from 82 to 323 K are measured for 1×1015  atom/cm2-implanted GaN annealed at 1100°C. Luminescence peaks at 356, 362, 376, 390, and 414 nm are observed on the 82 K cathodoluminescence spectrum. When the temperature is increased to 150 K, the intensities of the 356 and 414 nm peaks are nearly unchanged and the 362, 376, and 390 nm peaks disappear. The intensity ratio of 538 nm (H11/22→I15/24) and 559 nm (S3/24→I15/24) is increased with the increase in temperature. We try to shed light on the above interesting phenomena. Spatial distribution of crystalline quality in N-type GaN grown on patterned sapphire substrate Wide Bandap Semiconductor Technology Disciplines State Key Laboratory, School of Microelectronics, Xi'dian University, Xi'an 710071, China Optical Materials Express http://dx.doi.org/10.1364/OME.6.001817

The epitaxial layers of n-type GaN were grown on both planar and patterned sapphire substrate (PSS) by metal organic chemical vapor deposition.

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GANEX | Newsletter No. 41 - III-N Technology 29

By comparing the epitaxial layers grown on planar substrate, GaN grown on PSS exhibited many improvements both on surface morphology and crystalline quality according to the characterization of atoms force microscopy, and high resolution X-ray diffraction. Spatially resolved micro-Raman scattering results were performed for mapping the spatial variations in crystalline quality of the n-type GaN grown on PSS. According to the variations on the intensity and the full width at half maximum of GaN E2 (high) peaks, the crystalline quality improvement occurred in the lateral growth regions which correspond to center region of the pyramid patterns. We proposed that the bending of dislocations during the lateral growth plays an important role in the spatial variations of GaN crystalline quality. Cross sectional transmission electron microscope and spatial cathodoluminescence mapping results further supported the explanation of the dislocation inhibition during the growth process of GaN grown on PSS. Step-flow growth of GaN(0001) on 4H-SiC(0001) by plasma-assisted molecular beam epitaxy Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 412 96 Gothenburg, Sweden Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201533001

We report on step-flow growth of GaN(0001) on 4H-SiC(0001) substrates by plasma-assisted molecular beam epitaxy. The GaN layers were deposited directly on the substrate without using a buffer layer. A growth temperature of inline image and above resulted in an atomically flat surface morphology with locally straight steps indicating step-flow growth. The step height was 0.21 nm corresponding to one-half unit cell. The terrace width was 97 nm and the root-mean-square roughness was 0.06 nm. Samples grown below inline image exhibited a surface morphology consisting of spiraling terraces forming hexagonal hillocks. The full-width at half-maximum for X-ray rocking-curves recorded across the (0002) and (10inline image5) reflections was as narrow as 62 and 587 arcsec, respectively. We show that the high growth

temperature in conjunction with Ga adlayers on the growth front provides a path for achieving step-flow growth of GaN by MBE. Ultraviolet micro-Raman spectroscopy stress mapping of a 75-mm GaN-on-diamond wafer Materials Science, Engineering, and Commercialization, Texas State University, San Marcos, Texas 78666, USA Department of Physics, Texas State University, San Marcos, Texas 78666, USA Element Six Technologies, U.S. Corporation, Santa Clara, California 95054, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4952596

Full-wafer stress mapping is accomplished using visible and ultraviolet (UV) micro-Raman spectroscopy of a 730-nm thick GaN layer integrated with diamond grown by chemical vapor deposition. The UV measurements taken from both sides of the wafer reveal a higher tensile stress of 0.86 ±± 0.07 GPa at the free GaN surface compared to 0.23 ±± 0.06 GPa from the GaN/diamond interface, each with good cross-wafer uniformity. Factors influencing the overall stress and stress gradient are understood based on relaxation from dislocations in the GaN which vary in density along the growth direction. Simulations incorporating a model for stress relaxation in the GaN elastic modulus adequately describe the observed dependence. Infrared absorption of hydrogen-related defects in ammonothermal GaN Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4952388

Polarization controlled Fourier transform infrared (FTIR) absorption measurements were performed on a high quality m-plane ammonothermal GaN crystal grown using basic chemistry. The polarization dependence of characteristic absorption peaks of hydrogen-related defects at 3000–3500 cm−1 was used to identify and determine the bond orientation of hydrogenated defect complexes in the GaN lattice. Majority of hydrogen was found to be bonded in gallium

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GANEX | Newsletter No. 41 - III-N Technology 30

vacancy complexes decorated with one to three hydrogen atoms (VGa-H1,2,3) but also hydrogenated oxygen defect complexes, hydrogen in bond-center sites, and lattice direction independent absorption were observed. Absorption peak intensity was used to determine a total hydrogenated VGa density of approximately 4 × 1018 cm−3, with main contribution from VGa-H1,2. Also, a significant concentration of electrically passive VGa-H3 was detected. The high density of hydrogenated defects is expected to have a strong effect on the structural, optical, and electrical properties of ammonothermal GaN crystals. Enhanced photo/electroluminescence properties of Eu-doped GaN through optimization of the growth temperature and Eu related defect environment Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan APL Mater. http://dx.doi.org/10.1063/1.4950826

The influence of growth temperature on the surface morphology and luminescence properties of Eu-doped GaN layers grown by organometallic vapor phase epitaxy was investigated. By using a Eu source that does not contain oxygen in its molecular structure, and varying the growth temperature, the local defect environment around the Eu3+ ions was manipulated, yielding a higher emission intensity from the Eu3+ ions and a smoother sample surface. The optimal growth temperature was determined to be 960 °C and was used to fabricate a GaN-based red light-emitting diode with a significantly higher output power. Asymmetric skew X-ray diffraction at fixed incidence angle: application to semiconductor nano-objects Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany Laboratory for Applications of Synchrotron Radiation, Department of Physics, Karlsruhe Institute of Technology, Engesserstrasse 15, 76131 Karlsruhe, Germany

Journal of Applied Crystallography http://dx.doi.org/10.1107/S1600576716006385

A procedure for obtaining three-dimensionally resolved reciprocal-space maps in a skew X-ray diffraction geometry is described. The geometry allows tuning of the information depth in the range from tens of micrometres for symmetric skew diffraction down to tens of nanometres for strongly asymmetric skew geometries, where the angle of incidence is below the critical angle of total external reflection. The diffraction data are processed using a rotation matrix formalism. The whole three-dimensional reciprocal-space map can be measured by performing a single azimuthal rotation of the sample and using a two-dimensional detector, while keeping the angle of incidence and the X-ray information depth fixed (FIXD method). Having a high surface sensitivity under grazing-incidence conditions, the FIXD method can be applied to a large variety of Bragg reflections, particularly polar ones, which provide information on strain and chemical composition separately. In contrast with conventional grazing-incidence diffraction, the FIXD approach reveals, in addition to the lateral (in-plane) components, the vertical (out-of-plane) component of the strain field, and therefore allows the separation of the scattering contributions of strained epitaxial nanostructures by their vertical misfit. The potential of FIXD is demonstrated by resolving the diffraction signal from a single layer of InGaN quantum dots grown on a GaN buffer layer. The FIXD approach is suited to the study of free-standing and covered near-surface nano-objects, as well as vertically extended multilayer structures. Growth of GaN/InGaN Films and Heterostructures Via Super-Atmospheric MOCVD The University of North Carolina at Charlotte ECS Trans. http://dx.doi.org/10.1149/07205.0041ecst

In the interest of improving crystalline quality and optical performance of MOCVD grown semiconductors a unique super-atmospheric reactor was designed and fabricated. This reactor has since been used to fabricate GaN/InGaN

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GANEX | Newsletter No. 41 - III-N Technology 31

multi-quantum-well heterostructures under superatmospheric growth conditions. The resulting samples were analyzed through in-situ and ex-situ measurements. On the Origin of the 4.7 eV Absorption and 2.8 eV Emission Bands in Bulk AlN Substrates North Carolina State University ECS Trans. http://dx.doi.org/10.1149/07205.0031ecst

One of the main limitations based on point defects in AlN is related to the UV absorption band present at 265 nm. This relatively broad absorption band limits the use of bulk substrates within the deep UV range and several complicated fabrication procedures have been devised to overcome this limitation. The origin for this absorption band along with corresponding photoluminescence signatures will be reviewed. CN- and VN+ were identified as the point defects directly associated with the main absorption at 4.7 eV and the emission at 2.8 eV. The main absorption is due to a transition between the CN- state and conduction band, while the emission arises from a DAP transition between the donor VN+ and acceptor CN- through the 4.7 eV excitation channel. New observations based on photoluminescence excitation are presented to further support the assignments previously made. Epitaxial growth of GaN films on lattice-matched ScMgAlO4 substrates State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, Guangzhou 510640, China CrystEngComm http://dx.doi.org/10.1039/C6CE01071G

High-quality GaN films have been epitaxially grown on ScAlMgO4 (SCAM) (0001) substrates with an in-plane epitaxial relationship of GaN[1-100]//SCAM[1-100] by pulsed laser deposition (PLD). The effect of laser repetition rate on the qualities of GaN epitaxial films is studied in depth. It is found that as the laser repetition rate

increases from 10 to 40 Hz, the qualities of as-grown ~300 nm-thick GaN epitaxial films increase first and then decrease, and show the optimized values at the laser repetition rate of 30 Hz. The ~300 nm-thick GaN epitaxial films grown with the laser repetition rate of 30 Hz present very high crystalline quality with full-width at half-maximums of GaN(0002) and GaN(10-12) X-ray rocking curves of 0.18° and 0.40°, and reveal very smooth surface with a root-mean-square surface roughness of 1.5 nm. The as-grown GaN films also show an in-plane tensile stress of 0.51 GPa. Meanwhile, cross-sectional transmission electron microscopy confirms the sharp and abrupt GaN/SCAM hetero-interfaces. Near-White Emission observed in Dy doped AlN College of Chemistry, Jilin University, Changchun, China RSC Advances http://dx.doi.org/10.1039/C6RA03815H

AlN doped Dy phosphors were prepared by a simple solid state route, exhibiting excellent photoluminescence. The structure, composition and morphology were investigated by dint of X-ray diffraction, transmission electron microscope and energy-dispersive X-ray spectroscopy. Besides the characteristic emission of Dy, emission from AlN host could also be detected at room temperature. A post-thermal treatment under air atmosphere was employed to improve the photoluminescence. The blue emission and yellow emission from Dy ions contribute to the near near-white emission, possessing potential applications in white LED. Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China Scientific Reports http://dx.doi.org/10.1038/srep25124

Two AlGaN samples with different strain were designed to investigate mechanism of stress-driven composition evolution. It is discovered that AlGaN grown on AlN or (AlN/GaN superlattices

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(SLs))/GaN both consist of two distinct regions with different compositions: transition region and uniform region, which is attributed to the compositional pulling effect. The formation of the transition region is due to the partial stress release caused by the generation of misfit dislocations near the hetero-interface. And the Al composition in the uniform region depends on the magnitude of residual strain. The difference in relaxation degree is 80.5% for the AlGaN epilayers grown on different underlayers, leading to a large Al composition difference of 22%. The evolutionary process of Al composition along [0001] direction was investigated in detail. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556, USA Scientific Reports http://dx.doi.org/10.1038/srep24848

We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell.

A new approach to epitaxially grow high-quality GaN films on Si substrates: the combination of MBE and PLD State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China Scientific Reports http://dx.doi.org/10.1038/srep24448

High-quality GaN epitaxial films have been grown on Si substrates with Al buffer layer by the combination of molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) technologies. MBE is used to grow Al buffer layer at first, and then PLD is deployed to grow GaN epitaxial films on the Al buffer layer. The surface morphology, crystalline quality, and interfacial property of as-grown GaN epitaxial films on Si substrates are studied systematically. The as-grown ~300 nm-thick GaN epitaxial films grown at 850 °C with ~30 nm-thick Al buffer layer on Si substrates show high crystalline quality with the full-width at half-maximum (FWHM) for GaN(0002) and GaN(102) X-ray rocking curves of 0.45° and 0.61°, respectively; very flat GaN surface with the root-mean-square surface roughness of 2.5 nm; as well as the sharp and abrupt GaN/AlGaN/Al/Si hetero-interfaces. Furthermore, the corresponding growth mechanism of GaN epitaxial films grown on Si substrates with Al buffer layer by the combination of MBE and PLD is hence studied in depth. This work provides a novel and simple approach for the epitaxial growth of high-quality GaN epitaxial films on Si substrates. InGaN thin film deposition on Si(100) and glass substrates by termionic vacuum arc Department of Physics, Faculty of Art and Science, Muş Alparslan University, Muş, Turkey Journal of Physics: Conference Series http://dx.doi.org/10.1088/1742-6596/707/1/012019

Group-III nitride semiconductors covering infrared, visible and ultraviolet spectral range has direct band gaps changing from 0,7 eV (InN) to 3,4 eV (GaN). LEDs emit red, blue, green light, ultraviolet (UV) laser diodes (LD), UV light detectors and high power electronic devices are obtained and commercialized based on group-III

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nitride materials. InGaN semiconductor can be deposited by different techniques such as molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD). In this study, InGaN thin films were prepared on Si and glass substrates as well as on GaN layer by termionic vacuum arc (TVA) which is a plasma asisted thin film deposition technique. The film was deposited at 10-6 torr working pressure, 18A filament current. Plasma was produced at 200 V with 0,6A plasma current. The purpose of this research is to investigate the properties of InGaN thin films. X-ray diffraction (XRD) spectrophotometer was used to analyze microstructure of the deposited films. Scanning electon microscopy (SEM) were used for surface morphology characterizations. Compositional analysis was done by energy dispersive X-ray spectroscopy (EDAX). Surface acoustic wave velocity and elastic constants of cubic GaN Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Inés de la Cruz 3, E-28049 Madrid, Spain Applied Physics Express http://dx.doi.org/10.7567/APEX.9.061001

We present high-resolution surface Brillouin scattering measurements on cubic GaN layers grown on GaAs substrate. By using a suitable scattering geometry, scattering by surface acoustic waves is recorded for different azimuthal angles, and the surface acoustic wave velocities are determined. A comparison of experimental results with numerical simulations of the azimuthal dependence of the surface wave velocity shows good agreement and allows a consistent set of elastic constants for c-GaN to be determined. Effect of interface and bulk traps on the C–V characterization of a LPCVD-SiNx/AlGaN/GaN metal-insulator-semiconductor structure Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, People's Republic of China Semiconductor Science and Technology http://dx.doi.org/10.1088/0268-1242/31/6/065014

Silicon nitride (SiNx) film grown by low-pressure chemical vapor deposition (LPCVD) is utilized as a gate dielectric for AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Trap distribution at the gate-dielectric/III-nitrides interface is characterized by a temperature-dependent ac-capacitance technique. The extracted interface state density D it decreases from 2.92 × 1013 to 1.59 × 1012 cm−2 eV−1 as the energy level depth (E C-E T) increases from 0.29 to 0.50 eV, and then levels off to E C-E T = 0.80 eV. Capacitance-mode deep level transient spectroscopy (C-DLTS) and energy band diagram simulations reveal that deep levels with E C-E T > 0. 83 eV are responsible for the dispersion of capacitances at high temperature (>125 °C) and low frequencies (<1 kHz). A high-resolution transmission electron microscope (TEM) reveals that re-oxidation of the RCA-treated AlGaN barrier surface may be responsible for the relatively high density of shallow states at the LPCVD-SiNx/III-nitride interface. Electron microscopy analysis of microstructure of postannealed aluminum nitride template Malaysia–Japan International Institute of Technology (MJIIT), Universiti Teknologi Malaysia (UTM), Jalan Sultan Yahya Petra, 54100 Kuala Lumpur, Malaysia Applied Physics Express http://dx.doi.org/10.7567/APEX.9.065502

The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200 nm thickness on a sapphire (0001) substrate by metal–organic vapor phase epitaxy. The AlN template was annealed under (N2 + CO) atmosphere at 1500–1650 °C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure.

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Terahertz cyclotron resonance spectroscopy of an AlGaN/GaN heterostructure using a high-field pulsed magnet and an asynchronous optical sampling technique School of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, United Kingdom Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4948582

The effective mass, sheet carrier concentration, and mobility of electrons within a two-dimensional electron gas in an AlGaN/GaN heterostructure were determined using a laboratory-based terahertz cyclotron resonance spectrometer. The ability to perform terahertz cyclotron resonance spectroscopy with magnetic fields of up to 31 T was enabled by combining a high-field pulsed magnet with a modified asynchronous optical sampling terahertz detection scheme. This scheme allowed around 100 transmitted terahertz waveforms to be recorded over the 14 ms magnetic field pulse duration. The sheet density and mobility were measured to be 8.0 × 1012 cm−2 and 9000 cm2 V−1 s−1 at 77 K. The in-plane electron effective mass at the band edge was determined to be 0.228 ± 0.002m 0. Optical properties of nearly lattice-matched GaN/(Al,In)N quantum wells Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland J. Appl. Phys. http://dx.doi.org/10.1063/1.4951711

We report a systematic study of the photoluminescence (PL) properties of a series of nearly lattice-matched (LM) GaN/(Al,In)N single quantum well (SQW) samples, with well thickness ranging from 1.5 to 5 nm, grown by metalorganic vapor phase epitaxy. Temperature dependent PL and time-resolved PL measurements reveal similar trends among the studied SQW samples, which also indicate strong localization effects. The observed PL energy behavior, akin to the S-shape, accompanied first by a narrowing and then a broadening of the PL line width with increasing temperature, closely resemble previous

observations made on the more established (In,Ga)N/GaN QW system. The similar trends observed in the PL features of those two QW systems imply that the PL properties of LM GaN/(Al,In)N SQW samples are also governed by localized states. The effects of carrier transfer among these localization sites are clearly observed for the 3 nm thick QW, evidenced by an increasing PL intensity in the lower energy spectral window and a concomitant increase in the corresponding PL decay time. Time-resolved data corroborate the picture of strongly localized carriers and also indicate that above a well thickness dependent delocalization temperature carrier distribution across the localized sites reaches thermal equilibrium, as the PL decay times over different spectral regions converge to the same value. Based on the difference between the calculated QW ground state transition energy, obtained using the envelope wave function formalism, and the measured PL energy, a localization energy of at least a few hundreds of meV has been extracted for all of the studied SQW samples. This rather large value also implies that In-related localization effects are more pronounced in the GaN/(Al,In)N system with respect to those in the (In,Ga)N/GaN one for a similar In content. Studies of deep level centers determining the diffusion length in epitaxial layers and crystals of undoped n-GaN School of Advanced Materials Engineering and Research Center of Advanced Materials Development, Chonbuk National University, Jeonju 561-756, South Korea J. Appl. Phys. http://dx.doi.org/10.1063/1.4952734

A wide variety of parameters were measured for undoped n-GaN grown by hydride vapor phase epitaxy and compared to n-GaN films grown by conventional and lateral overgrowth metalorganic chemical vapor deposition. The parameters included deep level electron and hole trap spectra, microcathodoluminescence, electron beam induced current, diffusion length, and electron capture cross section from the dependence of the low temperature persistent

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photocapacitance on forward bias injection pulse duration. The results show a prominent role of electron traps with levels near Ec-0.56 eV in limiting the lifetime and diffusion length values in all these materials. Comparative study of single InGaN layers grown on Si(111) and GaN(0001) templates: The role of surface wetting and epitaxial constraint ETSIT-ISOM, Universidad Politécnica de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.04.007

This work presents a comparative study, based mainly on X-ray diffraction analysis, of compact (~100 nm thick) and uniform single crystal InGaN layers (In content <35%) grown by plasma-assisted molecular beam epitaxy. InGaN layers have been grown directly on Si(111) substrates and on commercially available GaN(0001)-on-sapphire templates.. A high reactivity of atomic N with Si leads to a formation of amorphous SiN on Si substrate, i.e. an indirect crystal-to-crystal InGaN/SiN/Si contact; the weak InGaN interaction with the underlying substrate (weak epitaxial constraint) further leads to poor surface “wetting” and consequent 3D nucleation. The InGaN growth on GaN is, on the other hand, characterized by a direct crystal-to-crystal InGaN/GaN contact; the strong InGaN interaction with the underlying substrate (strong epitaxial constraint) leads to good surface “wetting” and consequent 2D nucleation. All studied InGaN layers show single epitaxial relationship to both Si(111) and GaN(0001)-on-sapphire substrates as well as a relatively good compositional uniformity (no trace of InGaN phase separation). However, layers grown on Si show significantly lower strain and inferior crystallographic uniformity i.e. higher disorder in crystallographic tilt and twist. The surface “wetting” (poor vs. good) and epitaxial constraint (weak vs. strong) are suggested as the main origins of these discrepancies.

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PRESS RELEASE Technical and economic information selected by Knowmade

OPTOELECTRONICS

RayVio launches surface-mount UV LEDs for compact, portable disinfection of water and environments Semiconductor Today

RayVio Corp of Haywood, CA, USA, which is commercializing deep-ultraviolet (UV) LEDs and consumer disinfection solutions, has launched a new series of UV LEDs with what is claimed to be the highest power output available from a small surface-mount device (SMD) footprint. RayVio's technology enables the UV disinfection of water and environments via a new generation of powerful and portable health and hygiene devices. Read more Crystal IS expands range to high-powered UVC LEDs for disinfection of water, air and surfaces Semiconductor Today

Picture: Crystal IS' new Klaran UVC LED, a compact design targeting higher-power disinfection applications.

In hall A2 booth 213 at Analytica 2016 (the 25th International Trade Fair for Laboratory Technology, Analysis and Biotechnology), Crystal IS Inc of Green Island, NY, USA, an Asahi Kasei company that makes proprietary ultraviolet light-emitting diodes (UVC LEDs), has launched a commercial product line targeting higher-power

applications for UVC disinfection of water, air and surfaces. Read more LED market to grow at CAGR of nearly 17% until 2020 Semiconductor Today

The global LED market is expected to rise at a compound annual growth rate (CAGR) of nearly 17% until 2020, according to the report 'Global LED Market 2016-2020' from Technavio. The report covers four application segments - general lighting, backlighting, automotive lighting, and others – which in 2015 comprised 40.25%, 29.01%, 12.99%, and 17.75% of total revenue, respectively. "China supports the largest LED industry in the world and accounts for close to 30% of the world production, thanks to tax benefits and subsidies provided by the government to its manufacturers," says Asif Gani, one of Technavio's lead analyst for semiconductor equipment research. "The government of India has launched similar projects for promoting energy conservation, and it is likely to draw massive investments into the sector during the forecast period," he adds. Read more Vishay launches long-lifetime ceramic-based, high-power 365nm UV LED with silicone lens Semiconductor Today

Vishay Intertechnology Inc of Malvern, PA, USA has launched a new device in its VLMU35xx series of ceramic-based, high-power UV LEDs with

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silicone lenses that features a wavelength in the 365nm range for medical, industrial and printing applications. Designed to provide a reliable, energy-saving replacement for mercury lamps, the silicone lens of the Vishay Semiconductors VLMU3510-365-130 enables lifetimes up to 25,000hr, compared to the typical mercury lamp lifetime of 10,000hr. Read more Lumileds launches second-generation LUXEON CoB Compact Range LED arrays Semiconductor Today

LED maker Lumileds of San Jose, CA, USA has launched its second-generation LUXEON CoB Compact Range of LEDs, which feature an efficacy and output boost of up to 16% over its previous-generation arrays. Lumileds says that the new product line reinforces its position in chip-on-board technology by enabling cost-effective solid-state PAR, GU-10 and MR-16 lamps for retail, hospitality and home lighting applications. Read more Samsung's LED test lab approved for UL Total Certification Program Semiconductor Today

Samsung Electronics Co Ltd of Seoul, South Korea says that its test lab for LED packages and modules has been qualified by global safety science organization UL (Underwriters Laboratories) to operate the UL Total Certification Program (TCP), one of the highest levels of testing and qualification under the UL Data Acceptance Program (DAP). Read more

ELECTRONICS

Exagan partners with HIREX to establish GaN-on-Si's reliability for power converters Semiconductor Today

Gallium nitride (GaN) technology start-up Exagan of Grenoble, France has begun a strategic partnership to develop and commercialize GaN-on-silicon products with HIREX Engineering, a company of Alter Technology Group (TÜV Nord Group's Aerospace and Electronics business unit). TÜV NORD is a multi-national technical services provider to aerospace, industrial, mobile communications and IT markets Read more Exagan showcasing GaN-on-Si technology and announcing strategic partnership at PCIM Europe Semiconductor Today

In booth #9-230 at the PCIM (Power Conversion Intelligent Motion) Europe 2016 trade show in Nuremberg, Germany (at 11:30am on 10 May), Exagan of Grenoble, France, a gallium nitride (GaN) technology start-up that enables smaller and more efficient electrical converters, will announce its latest strategic partnership to develop and commercialize GaN-on-silicon products. Read more 650V GaN FET with the lowest R(on) in a TO-247 Power Electronics

Transphorm has introduced the TPH3207WS GaN field effect transistor (FET) with the lowest on-resistance (41 mW) in a TO-247 package that reduces system volume as much as 50% without sacrificing efficiency. The device’s low RDS(ON)

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and ultra-low Qrr (175nC) bring the benefits of GaN to applications that previously relied on silicon, enabling engineers to achieve power-dense solutions with reduced component count and improved reliability in high-voltage power conversion applications. Read more Development Boards Use GaN FETs and High Frequency Synchronous Bootstrap Power Electronics

Efficient Power Conversion has introduced the EPC9066, EPC9067, and EPC9068 development boards, which are configurable to a buck converter or as a ZVS class-D amplifier. These boards provide an easy-to-use way for power systems designers to evaluate the exceptional performance of gallium nitride transistors, enabling the designers to get their products into volume production quickly. Read more Gallium Nitride Looks to Widen its Footprint in the Global Power Semis Industry Power Electronics

Michael Markides, director of power and utilities at IHS Technology attended this year's American Power Electronics Conference (APEC) in Long Beach, California. The IHS Power team dove into key industry topics like the ever-increasing electrification of automobiles, expected growth from smart energy applications, and the total market slowdown that began in the second half of 2015. The most notable topic, however, was the presence of many gallium-nitride (GaN) specialist suppliers and their optimism this new technology will at last be rapidly adopted in the market. Read more Qorvo launches GaN-on-SiC PAs for military radar, communications and electronic warfare applications Semiconductor Today

Qorvo Inc of Greensboro, NC and Hillsboro, OR, USA (which provides core technologies and RF solutions for mobile, infrastructure and aerospace/defense applications) has launched three gallium nitride on silicon carbide (GaN-on-SiC) power amplifiers (PAs) optimized for use in

military radar, communications and electronic warfare (EW) systems:

TGM2635-CP – an X-band 100W MMIC amplifier operating at 7.9-11GHz for satellite communications, data links and radar applications that provides 50dBm of saturated output power, with 22.5dB of large signal gain and 35% power-added efficiency (PAE). Available in a pure copper-base bolt-down package, the TGM2635-CP offers superior thermal management for added system flexibility.

TGA2307-SM – a C-band 50W MMIC amplifier operating at 5-6GHz that produces more than 47dBm of saturated output power with a PAE greater than 44% and a large-signal gain greater than 20dB. Packaged in a small low-cost 6mm x 6mm plastic overmold QFN package, the TGA2307-SM provides size, weight and power (SWAP) benefits for C-band radar applications.

TGA2963 – a 20W wideband MMIC amplifier (in die form) operating at 6-18GHz for wideband communication platforms, radar systems, electronic warfare and test instrumentation that provides more than 43dBm saturated output power with PAE of more than 20% and a large-signal gain greater than 20dB.

Read more Qorvo and NanoSemi demo ultra-wideband linearization for massive MIMO applications Semiconductor Today

In conjunction with NanoSemi Inc of Waltham, MA, USA (a developer of digital linearization and compensation algorithms), Qorvo Inc of Greensboro, NC and Hillsboro, OR, USA (which provides core technologies and RF solutions for mobile, infrastructure and aerospace/defense applications) says that it has demonstrated industry-leading ultra-wideband linearization results with its gallium nitride (GaN) power amplifiers for wireless infrastructure. Read more

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Qorvo's new GaN 50V transistors boost power gain and efficiency for wideband defense and commercial radar, communications and avionics Semiconductor Today

Qorvo Inc of Greensboro, NC and Hillsboro, OR, USA (which provides core technologies and RF solutions for mobile, infrastructure and aerospace/defense applications) has launched six 50V gallium nitride (GaN) transistors designed to optimize power performance for commercial and defense radar, communications systems and avionics. Read more Qorvo's GaN transistor passes stringent environmental tests, proving readiness for public safety and defense applications Semiconductor Today

Qorvo Inc of Greensboro, NC and Hillsboro, OR, USA (which provides core technologies and RF solutions for mobile, infrastructure and defense applications) says that its 15W gallium nitride on silicon carbide (GaN-on-SiC) wideband input-matched transistor has completed stringent environmental testing, demonstrating its reliability for use in defense and emergency response communications equipment. Read more MACOM launches 300W plastic-packaged GaN-on-Si power transistor for commercial RF energy applications Semiconductor Today

MACOM Technology Solutions Holdings Inc of Lowell, MA, USA (which makes semiconductors, components and subassemblies for analog RF, microwave, millimeter-wave and photonic applications) has launched the MAGe-102425-300, a 300W gallium nitride on silicon (GaN-on-Si) rugged power transistor in cost-effective plastic packaging optimized for use in commercial-scale solid-state RF energy applications. Based on MACOM's Gen4 GaN technology, the MAGe-102425-300 delivers performance that defies the inherent power efficiency and density limitations of LDMOS at an equivalent price profile at scaled volume production levels, says the firm. Read more

MACOM to demo Gen4 GaN-on-Si portfolio at IMS Semiconductor Today

In booth 939 at IEEE's International Microwave Symposium (IMS) 2016 in San Francisco (24-26 May), MACOM Technology Solutions Holdings Inc of Lowell, MA, USA (which makes semiconductors, components and subassemblies for analog RF, microwave, millimeter-wave and photonic applications) is showcasing its GaN-on-Si (gallium nitride on silicon) portfolio and other high-performance products, optimized for commercial, industrial, scientific and medical RF applications:

a GaN 60W average-power Doherty module live demonstration with Xilinx DPD (digital pre-distortion) for base-station applications;

a GaN for RF energy applications;

new E-band TX and RX SMD modules and portfolio of wideband millimeter-wave products for addressing the emerging 5G access and backhaul markets;

high-power (120W), broadband PIN diode transmit-receive (T/R) switch demonstrating low TX IL, low RX IL, high RX isolation, small physical size, plastic SMT package across DC-1GHz for MILCOM and land mobile applications;

a W-band power amplifier monolithic microwave integrated circuit (MMIC) covering 80-100GHz with what is claimed to be leading gain and power performance; and

high-reliability and component products for mission-critical space and aerospace applications.

Read more MACOM's latest 320W and 160W plastic-packaged GaN power transistors achieve 79% efficiency for wireless base-stations Semiconductor Today

MACOM Technology Solutions Holdings Inc of Lowell, MA, USA (which makes semiconductors, components and subassemblies for analog RF, microwave, millimeter-wave and photonic applications) has launched the newest entries in its MAGb series of gallium nitride-on-silicon (GaN-on-Si) power transistors for use in macro wireless base-stations. Based on MACOM's Gen4 GaN technology, the MAGb-101822-240B0P and MAGb-101822-120B0P power transistors harness

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the performance benefits of GaN in rugged, low-cost plastic packaging, enabling improved cost efficiencies over legacy LDMOS silicon for base-station applications, says MACOM. Read more Wolfspeed highlighting GaN-on-SiC RF HEMTs at IMS 2016 Semiconductor Today

In booth #1621 at the IEEE International Microwave Symposium (IMS 2016) in San Francisco (May 22–27), Wolfspeed of Research Triangle Park, NC, USA — a Cree Company that makes GaN-on-SiC high-electron-mobility transistors (HEMTs) and monolithic microwave integrated circuits (MMICs) — is highlighting its latest RF and microwave devices and foundry services. The firm is also supporting the IMS 2016 STEM (Science, Technology Engineering & Math) program, and several on-site student design competitions. Read more IQE transfers Translucent's cREO growth capability to North Carolina facility Semiconductor Today

At the International Conference on Compound Semiconductor Manufacturing Technology (CS MANTECH 2016) in Miami, FL, USA (16-18 May), epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK has announced two key developments. Transfer of cREO growth technology to North Carolina facility […] Demonstration of interface charge tuning using cREO for GaN products […] Under the terms of the license and assignment agreement signed last September, IQE has 30 months in which to decide to acquire Translucent's technology with the payment of a further $5m. Upon commercialization of the technology, a perpetual royalty of 3-6% of IQE's revenues generated from the technology would be payable to Translucent. Read more

IQE joins imec's GaN-on-Si Industrial Affiliation Program Semiconductor Today

Epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK has announced a strategic partnership on gallium nitride-on-silicon (GaN-on-Si) technology with nanoelectronics research centre imec of Leuven, Belgium.

Picture: Forward and reverse diode current at high temperature (150◦C). The diodes have 10mm anode width and an anode-to-cathode distance of 10µm.

GaN technology offers faster power-switching devices with higher breakdown voltage and lower on-resistance than silicon, suiting advanced power electronic components. The partnership builds on promising results achieved in a recent project, in which imec and IQE collaborated to fabricate GaN power diodes using imec's proprietary diode architecture and IQE's high-voltage epiwafers. Read more NXP launches GaN transistors for EW and communication systems Semiconductor Today

NXP Semiconductors N.V. of Eindhoven, The Netherlands has expanded its portfolio of broadband gallium nitride (GaN) RF power transistors suitable for electronic warfare (EW) and battlefield radio applications, including launching six new driver or final-stage amplifiers with frequency coverage as broad as 1-3000MHz. Read more

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NXP launches GaN RF power transistors optimized for Doherty amplifiers in cellular base-stations Semiconductor Today

NXP Semiconductors N.V. of Eindhoven, The Netherlands has announced an expansion to its portfolio of 48V gallium nitride (GaN) RF power transistors optimized for Doherty power amplifiers for use in current and next-generation cellular base-stations. The four new transistors collectively cover cellular bands from 1805MHz to 3600MHz, meeting the needs of wireless carriers for superior performance at higher frequencies. Read more GaN showcasing customers' systems using its transistors at PCIM Europe Semiconductor Today

In booth # 9-511 at PCIM (Power Conversion Intelligent Motion) Europe 2016 in Nuremberg, Germany (10-12 May), GaN Systems Inc of Ottawa, Ontario, Canada, a fabless developer of gallium nitride (GaN)-based power switching semiconductors for power conversion and control applications, is showcasing a lineup of its customers' systems that are enabled by gallium nitride transistors. The customer products featured include:

a 1kW energy storage system that is 50% smaller than prior silicon-based solutions;

high-current power modules used in the industrial and automotive industries;

a 1.2kW battery charger that delivers 33% more power in the same volume as its silicon predecessor;

a 12kW stop-start generator showcasing a 5x size reduction;

a >97% efficient, ultra-compact electric vehicle (EV) charger;

a multi-voltage, high-speed 1.5kW motor controller; and

a high-power, high-efficiency traction inverter using GaN power modules.

In addition to commercial products, GaN Systems is exhibiting the inverter enabled by its transistors which recently won Google's Little Box Challenge. The team Red Electrical Devils from CE+T Power of Wandre, Belgium, won the US$1m first prize for designing, building, and demonstrating an inverter with the highest power density in the smallest

volume: 143W/cubic inch in only 14 cubic inches. Also on show is be a half-bridge evaluation board that simplifies GaN transistor testing. Read more Richardson RFPD to distribute GaN Systems' power devices Semiconductor Today

Richardson RFPD Inc (an Arrow Electronics company) – which specializes in the RF and wireless communications, power conversion and renewable energy markets – has agreed to sell the gallium nitride in silicon (GaN-on-Si) power devices of GaN Systems Inc of Ottawa, Ontario, Canada, on a global basis, excluding Israel. Read more Intersil extending radiation-tolerant portfolio to GaN power conversion ICs for satellite applications Semiconductor Today

Intersil Corp of Milpitas, CA, USA, a provider of power management and precision analog solutions, says that it plans to extend its radiation-tolerant portfolio to include gallium nitride (GaN) power conversion ICs for satellites and other harsh-environment applications. Intersil intends to couple its radiation-hardened field-effect transistor (FET) drivers with GaN FETs to deliver performance that leapfrogs existing products that rely on traditional high-reliability FET technologies. GaN provides better conductivity and switching characteristics that enable several system benefits, including a reduction in system power losses. Read more Microsemi showcasing 15 new RF, microwave and millimeter-wave devices Semiconductor Today

Microsemi Corp of Aliso Viejo, CA, USA (which makes chips for the communications, security, aerospace and industrial markets) is featuring 15 new products from its radio frequency (RF), millimeter-wave integrated circuit (IC), monolithic microwave integrated circuit (MMIC), ultra-low-power sub-GHz transceiver and high-performance WLAN monolithic radio frequency integrated circuit (RFIC) portfolio at the IEEE MTT-S

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International Microwave Symposium (IMS2016) in San Francisco (22-27 May). With a broad product offering spanning the DC to 140GHz frequency range, the new devices build on Microsemi's history in RF, microwave and millimeter-wave solutions and meet the growing demand in the defense, communications, instrumentation, industrial and aerospace industries. […] GaN HEMT RF power transistors and drivers covering L-band to 750W Microsemi's expanding family of RF power transistors based on gallium nitride (GaN) high-electron-mobility transistors (HEMTs) on silicon carbide (SiC) substrates includes six new L-band RF power transistors and drivers rated between 120W and 750W. The new 1214GN-750V, 1214GN-120E/EL/EP, 1011GN-125E/EL/EP, 1011GN-250E/EL/EP, 1416GN-600V and 1416GN-120E/EL/EP RF power transistors and drivers span a wide range of radar, avionics and communications applications with compact packaging options. [….] Read more Diamond Microwave launches GaN X-band SSPAs with integrated monitoring and protection Semiconductor Today

Diamond Microwave Devices Ltd of Leeds, UK (which specializes in high-performance microwave power amplifiers) has launched a range of X-band gallium nitride (GaN)-based pulsed solid-state power amplifiers (SSPA) offering integrated monitoring and protection. Read more Peregrine's MPAC-Doherty device demonstrated optimizing RFHIC's GaN Doherty amplifier at 3.5GHz Semiconductor Today

In booth #2129 at the IEEE's International Microwave Symposium (IMS 2016) in San Francisco (24-26 May), Peregrine Semiconductor Corp of San Diego, CA, USA – a fabless provider of radio-frequency integrated circuits (RFICs) based on silicon-on-insulator (SOI) – is demonstrating a monolithic phase and amplitude controller (MPAC)–Doherty with a gallium nitride (GaN)

Doherty amplifier from RFHIC Corp of Anyang-Si, South Korea (which is exhibiting in booth #821). Read more Akoustis presenting AlGaN-on-Si BAW filter technology at RFIC Symposium Semiconductor Today

Akoustis Technologies Inc of Huntersville, NC, USA (in the Piedmont technology corridor between Charlotte and Raleigh), which manufactures patent-pending BulkONE single-crystal piezoelectric bulk acoustic wave (BAW) RF filters for mobile wireless applications, says that chief device scientist Dr Rama Vetury is a featured presenter at the IEEE Radio Frequency Integrated Circuits Symposium (RFIC 2016) in San Francisco, CA, USA (22-24 May) as part of Microwave Week 2016. The presentation takes place on 23 May in session RMO2A-1 (10.10-10.30am PST) at the Marriott Salons 1–3. Read more Panasonic showcases GaN-based technologies at PCIM Europe Semiconductor Today

At the PCIM (Power Conversion Intelligent Motion) Europe 2016 event in Nuremberg, Germany (10-12 May), Panasonic Automotive & Industrial Systems Europe showcased its technology lineup, highlighting innovations including passive components, semiconductors and thermal management solutions that provide increased efficiency and reliability for a wide range of applications. These included an X-GaN gate driver. Read more Ampleon launches second generation of 50V, 0.5μm GaN-on-SiC RF power transistors Semiconductor Today

Ampleon Netherlands B.V. of Nijmegen, The Netherlands (formerly NXP Semiconductors N.V.'s RF Power business, acquired by China's Jianguang Asset Management Co Ltd last December) has launched its second generation of 50V, 0.5μm gallium nitride on silicon carbide (GaN-on-SiC) RF power transistors, dedicated for mobile broadband applications. Read more

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Cobham launches family of solid-state radar transmitters Semiconductor Today

Picture: Cobham's new GaN-based solid-state transmitter.

UK-based Cobham has launched a scalable family of gallium nitride (GaN) solid-state transmitter solutions. SOLSTx (pronounced 'solstice') is optimized for ground, maritime and airborne applications including air-traffic control, weather, telemetry, fire control, and long-range surveillance radars. Read more TMD giving live demos of new GaN MMIC-based microwave power modules at IMS2016 Semiconductor Today

In booth 1849 at the IEEE International Microwave Symposium (IMS2016) in San Francisco (24-26 May), UK-based TMD Technologies Ltd is giving daily live demonstrations of its new PTS6900 solid-state microwave power module (MPM) – a gallium nitride (GaN) monolithic microwave integrated circuit (MMIC)-based module optimized for EW/ECM (electronic warfare/electronic countermeasure) systems. Read more Comtech Xicom launches compact 20W GaN X-band SATCOM block upconverter Semiconductor Today

Comtech Xicom Technology Inc of Santa Clara, CA, USA, which makes tube-based and solid-state power amplifiers for military and commercial satellite communication (SATCOM) uplink applications, has launched a gallium nitride (GaN)-based solid-state X-band block upconverter (BUC) in a 5.3-pound (2.4kg) antenna-mount outdoor unit. The compact and lightweight BUC provides 20W of linear output power in a 5.8» x 5.1» x 3.9»

(147mm x 130mm x 99mm) feed-mountable package designed to handle tough environments and meet stringent X-band RF requirements, while drawing very little power for extended battery operation. Read more Pasternack launches 50W GaN coaxial power amplifier operating at 2-6GHz Semiconductor Today

Pasternack Enterprises Inc of Irvine, CA, USA (which makes both passive and active RF, microwave and millimeter-wave products) has launched the PE15A5025, a 50W gallium nitride (GaN) coaxial power amplifier operating in the 2-6GHz frequency band. The compact and rugged design delivers high levels of output power and efficiency and has high output load impedance, making port matching easier over wider bandwidths using lower-loss components. Applications include commercial and military radar, jamming systems, medical imaging, wireless communications and electronic warfare. Read more

OTHER

Sandia qualifies and accepts Nippon Sanso's SR-4000HT commercial MOCVD system Semiconductor Today

Matheson Tri-Gas Inc of Basking Ridge, NJ, USA, together with its parent company industrial gas supplier Taiyo Nippon Sanso Corp (TNSC) of Tokyo, Japan, says that Sandia National Laboratories has qualified and accepted the SR-4000HT commercial-grade gallium nitride (GaN) metal-organic chemical vapor deposition (MOCVD) system for its continued compound semiconductor device developmental work with aluminium gallium nitride (AlGaN) and aluminium nitride (AlN). Read more

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Aixtron agrees €670m takeover by Fujian Grand Chip Investment Fund Semiconductor Today

Deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany has entered into an agreement for Grand Chip Investment GmbH (CGI), an indirect subsidiary of Fujian Grand Chip Investment Fund LP (FGC), to take it over. Fujian Grand Chip Investment Fund LP is a Chinese investment fund, 51% of which is held by Chinese businessman and private investor Zhendong Liu and 49% by Xiamen Bohao Investment Ltd (an investment entity indirectly controlled by Chinese private investors Zhongyao Wang and Wanming Huang). Read more Aixtron's Q1 revenue hit by ongoing weak LED-related demand Semiconductor Today

For first-quarter 2016, deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany has reported revenue of €21.4m, almost halving (down 47%) from €40.3m a year ago and down by almost two-thirds (62.5%) from last quarter's €62.5m. This was due in particular to the ongoing weak demand for production systems for gallium nitride (GaN)-based LED applications and the corresponding low order intake in Q3/2015 and Q4/2015.

Of total revenue, 56% came from equipment sales and 44% (€9.5) from sales of spare parts & services (much higher than normal due to the very low product sales). On a regional basis, over 70% of revenue came from Asia, 13% from Europe, and 17% from the USA. Read more Riber's Q1 revenue almost halves year-on-year Semiconductor Today

Riber S.A. of Bezons, France, which manufactures molecular beam epitaxy (MBE) systems as well as evaporation sources and effusion cells, recently said that its quarterly revenue had almost halved year-on-year from €2.7m in first-quarter 2015, down 52% to €1.4m in first-quarter 2016 (30% from Asia, 33% from Europe, 37% from the USA). While no revenue was recorded for MBE systems (compared with €1.5m a year ago), this reflects a delivery schedule for system orders that is focused on second-half 2016 and is not indicative of the firm's performance over the full year. Read more Riber to sell part of facility after losses grow in 2015 Semiconductor Today

For full-year 2015, Riber S.A. of Bezons, France, which manufactures molecular beam epitaxy (MBE) systems as well as evaporation sources and effusion cells, has reported revenue of €12.8m, down 23% on 2014's €16.6m. This is due in particular to MBE System revenue falling by 34% from €9.3m to €6.1m. Over the full year, just nine R&D systems were delivered and

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invoiced (including four in fourth-quarter 2015), down on 11 in 2014. Read more Rubicon's revenue rebounds, driven by 6" patterned sapphire substrates Semiconductor Today

For first-quarter 2016, Rubicon Technology Inc of Bensenville, IL, USA (which makes monocrystalline sapphire substrates and products for the LED, semiconductor and optical industries) has reported revenue of $4.3m, down on $8.9m a year ago but up on $2.45m last quarter. The rise was due primarily to wafer revenue rising by $1.5m from $0.86m to $2.35m, mostly from 6-inch diameter patterned sapphire substrates (PSS) for the LED market rising by $1.1m from $0.4m to $1.5m, while polished wafers rose from $0.45m to $0.83m (though down on $1.4m a year ago). R&D revenue was steady at about $0.1m (down slightly on $0.14m a year ago). Although it is still down on $1.8m a year ago, optical revenue rose from $1m to $1.4m. Revenue from core sales has fallen further from $5.1m a year ago and $0.48m last quarter to $0.44m. Apart from just $2000 of 2-inch cores (down from $10,000 last quarter and $4m a year ago), nearly all of this was from 4-inch cores for the LED market (down slightly from $0.47m last quarter and $1m a year ago). Despite the fact that the LED market continues to grow and some competitors have left the market, excess sapphire capacity continues to keep pricing at historically low levels, especially for 2- and 4-inch cores. Hence, in recent quarters, Rubicon has been limiting the amount of 2- and 4-inch core sold. Read more

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PATENT APPLICATION

More than 200 new patent applications were published between 2016-05-02 and 2016-06-01.

Patent Applicants Number of new patent applications

LG Innotek 8

Xiamen Changelight 5

CEA - The French Alternative Energies and Atomic Energy Commission 5

Toyoda Gosei 4

Samsung Electronics 4

Stanley Electric 4

University of Tokyo 4 Other patent applicants: 13th Research Institute Of China Electronics Technology, Alcatel Lucent, Applied Materials, Asahi Chemical Industry, Carl Zeiss, Chengdu New Keli Chemical Science, China Bright Photoelectricity, China Three Gorges University, Chonbuk National University Industry Academy Cooperation Foundation, Dalian University of Technology, Dalian Dehao Photoelectric Technology, Delta Electronics, Denso, Dongguan Qingmaitian Digital Technology, Dowa Electronics Materials, Electronics & Telecommunications Research Institute (ETRI), Enraytek Optoelectronics, Focus Lightings Technology, Foshan Guoxing Semiconductor Technology, Foshan Xinguang Semiconductor, Fujitsu, Furukawa, Guangdong Deli Photoelectric, Harbin Institute of Technology, HC Semitek, Hong Kong University of Science and Technology, Hongik University Industry Academia Cooperation Foundation, Huazhong University of Science & Technology, Hunan Hiend Products, IBM, Iljin LED, Industrial Technology Research Institute (ITRI), Infineon Technologies, Institute Basic Science, Institute of Physics Chinese Academy Of Sciences, Intel, Korea Advanced Nano Fab Center, Kunshan Yong Xuzhi Wealth Technology Service, Ledst, Lightwave, Mitsubishi Chemical, Mitsubishi Electric, Nagoya Institute of Technology, Nanjing Jinmei Callium, Nanjing University of Posts & Telecommunications, Nanjing University of Technology, Nantong Tongfang Semiconductor, National Sun Yat-Sen University, NGK Insulators, Nichia, Nippon Telegraph & Telephone (NTT), No 55 Institute of China Electronics Science & Technology, Osram Opto Semiconductors, Panasonic, Postech Foundation, Rongchuang Energy Technology, Samsung Display Devices, Sanan Optoelectronics, Sanken Electric, Sensor Electronic Technology, Seoul Viosys, Shandong Tide China Light Photoelectron, Shanghai Core Stone Microelectronics, Shinetsu Handotai, Sim Jae, Sino Nitride Semiconductor, Soitec, South China Normal University, South China University of Technology, Sumitomo Chemical, Sumitomo Electric Industries, Suzhou Dynax High Energy Semiconductor, Suzhou Jingzhan Semiconductor, Taiwan Semiconductor Manufacturing (TSMC), Tamura Seisakusho, Texas Instruments, Tokuyama, Toshiba, Toshiba Lighting & Technology, Unist Academy Industry Research, University Beijing, University Dongguk, University of Electronic Science & Technology of China, Waseda University, Wisconsin Alumni Research Foundation, Xi An Shiyou University, Xiangneng Hualei Optoelectronic Corppration, Xidian University, Yangzhou Haike Electronic Technology, Zhang Zhigang, Zhanjing Technology, Zhu Bingchen …

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New patent applications selected by Knowmade Patterned back-barrier for iii-nitride semiconductor devices Publ. Nb: US2016141354, DE102015119515, CN105609550 Patent Applicant: Infineon Technologies (AT)

A compound semiconductor device includes a III-nitride buffer and a III-nitride barrier on the III-nitride buffer. The III-nitride barrier has a different band gap than the III-nitride buffer so that a two-dimensional charge carrier gas channel arises along an interface between the III-nitride buffer and the III-nitride barrier. The compound semiconductor device further includes a source and a drain spaced apart from one another and electrically connected to the two-dimensional charge carrier gas channel, a gate for controlling the two-dimensional charge carrier gas channel between the source and the drain, and a patterned III-nitride back-barrier buried in the III-nitride buffer. The patterned III-nitride back-barrier extends laterally beyond the gate towards the drain and terminates prior to the drain so that the patterned III-nitride back-barrier is laterally spaced apart from the drain by a region of the III-nitride buffer. Read more Gallium nitride on high thermal conductivity material device and method Publ. Nb: US9337278 Patent Applicant: Qorvo (US)

Embodiments include but are not limited to semiconductor devices including a barrier layer, a gallium nitride channel layer having a Ga-face coupled with the barrier layer, and a thermoconductive layer having a thermal conductivity of at least 500 W/(m·K) within 1000 nanometers of a Ga-face of the gallium nitride channel layer. The semiconductor device may be a high-electron-mobility transistor or a semiconductor wafer. Methods for making the same also are described. Read more

Flexible arrays of micro light emitting diodes using a photoelectrochemical (pec) liftoff technique Publ. Nb: WO2016069766 Patent Applicant: University Of California (US)

Flexible arrays of III-nitride micro light-emitting diodes (LEDs) are fabricated using a photoelectrochemical (PEC) etch as a liftoff technique. A sacrificial layer is grown on a host substrate, wherein the sacrificial layer comprises a III-nitride layer and the host substrate comprises a bulk gallium nitride (GaN) substrate. A III-nitride device structure is then grown on or above the sacrificial layer. A submount is prepared with a polymer film deposited thereon, and the device structure is flip-chip bonded onto the polymer film of the submount. The sacrificial layer is removed using the PEC etch to separate the host substrate from the device structure bonded to the polymer film of the submount. Finally, the polymer film with the device structure is de-laminated from the submount. Read more

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Semiconductor light-emitting device Publ. Nb: WO2016072277, JP2016092286 Patent Applicant: Stanley Electric (JP), University of Tokyo (JP)

A semiconductor light-emitting device comprises: a first semiconductor layer having a first conductivity type; a light-emitting function layer including a light-emitting layer formed on the first semiconductor layer; and a second semiconductor layer formed on the light-emitting function layer and having an opposite conductivity type to the first semiconductor layer. The light-emitting layer comprises: a base layer having such compositions that experience a stress strain from the first semiconductor layer and having a plurality of base segments formed like a random mesh; and a quantum well structure layer consisting of at least one quantum well layer, which is formed in such a manner that embeds the base layer, and at least one barrier layer. The base layer has a plurality of subsidiary base layers composed of AlGaN's having mutually different Al components. Read more

CMOS circuits using n-channel and p-channel gallium nitride transistors Publ. Nb: WO2016080961 Patent Applicant: Intel (US)

CMOS circuits may formed using p-channel gallium nitride transistors and n-channel gallium nitride transistors, wherein both the p-channel gallium nitride transistors and the n-channel gallium nitride transistors are formed on a single layered structure comprising a polarization layer deposited on a first gallium nitride layer and a second gallium nitride layer deposited on the polarization layer. Having both n-channel gallium nitride transistors and p-channel gallium nitride transistors s on the same layer structure may enable "all gallium nitride transistor" implementations of circuits including logic, digital, and analog circuitries spanning low supply voltages to high supply voltages. Read more

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