MBE Growth of III-V Materials and its Applications
to 2D/1D/0D Nanostructured Devices
•Constraint of carriers by heterostructure affects the physical characteristics of devices. •With it, researchers have put quantum physics in practice to enhance and modify the properties of devices. Constraint of carriers can be classified by degree of restriction of dimensions. As a result, carriers can move freely in 2 (1 and 0) dimensional space with 1 (2, and 3) dimensional constraint(s), respectively. •Naturally, not only introduction of new structures but also new materials, such as Sb-based 3-5 materials, can be resource of new idea. •In this presentation, the authors will show various MBE-grown 2D, 1D and 0D-structures. Low density large droplet quantum dots (QDs), long wavelength type-2 InSb QDs on InAs substrate, and short wavelength InP/InGaAs QDs (Dashes) will be discussed for 0 D-structures, and (In)GaAs nano-wires on (111) Si will be shown for 1D-structure. Finally, electrical properties type-2 quantum wells for p-type will be presented for 2D-structures.
•We are happy to work with co-workers in the world
Conclusion
• Riber compact 21 cluster MBE systems: 3MBEs+1E-beam evaporator + 1 Sputter [In/Ga/Al + As/P/Sb + Be/Si/GaTe]
• VG 80 cluster MBE systems: 2 MBEs [In/Ga/Al + As/P + Be/Si]
• VEECO 930 MBE [In/Ga/Al + As/P + Be/Si/C]
• Home-made MBE (under construction) [In/Ga/Al + N + Be/Mg]
3 Dimensional structures (artificial bulk, new materials) 2 Dimensional structures (type-1,-2 QWs)
In these MBE systems, all generation of 3-5 materials are grown.▲
High quality InSb (~ 70,000 cm2/Vs @ 300K, 2.6um) were grown on GaAs or Si wafers using InAs interlayers. High-quality thin InSb (0.4 um) were obtained by grading InAlSb buffers. ▲
All kind of Sb-As based ternary compound were grown. Sb-P based materials are under research. ◄
Digital alloy InGaAlAs were grown by repetition of short period superlattices of few monolayer thick-InGaAs and InAlAs.▲
This artificial bulk materials can be used for 1.3um QWs, uniform DBR, QCL lasers. ▼
InAs/InGaAs/InAlAsHEMT structure achieved the mobility of 14,000 cm2/Vs at 300 K and ~140,000 cm2/Vs at 77K. ◄
This structure was used for the implementation of Spin-FET.
Formation of InSbwell is confirmed. More in-depth study is necessary for real application. ◄
(electron mobility @ RT ~ 20,000 cm2/Vs, Ns ~ 1.5E12/cm2)
Cf) Target is > 40,000 cm2/Vs @ RT
Sb-based type-2 QW shows large mobility of 2DEG/ 2DHG which are critical for low power consumption devices. ◄
1/1000 of power consumption is expected with implementation of 3-5 CMOS with this structure.
GaAs nano rods grown by Ga-droplets (Catalyst-free Nano wires) were successfully achieved on (100) GaAs.◄
This nano rods has perfect ZB structures without contamination of WZ structures.
1 Dimensional structures
Gold nano-particles were used as a catalyst for 3-5 nano rods. Nano rods were grown on (111) Si substrates with gold nano-particles. ◄
The GaAs Nano rods shows perfect WZ without contamination of ZB structures.
The nano-rods can be used for perfect anti-reflects.
Various nano rods such as In(AsPSb) and Ga(AsPSb) nano rods are prepared or under research for single photon source or 1D electronic devices.
0 Dimensional structures
Conventional SK-mode grown In(Ga)As QDs are grown on GaAs, Si. These were used for solar cell, QDIP (IR sensor) etc. ▲
Very low density ( few QDs/um2) InAs QDs were grown for quantum physics studies. ◄
With GaAs/AlGaAs droplet QDs, we can grow QDs, Q-rings, Q-disks, and Q-pits. ▲
This structure can be used for template of new noble structures such as artificial molecules. ▼
MEE-mode grown InAs, InGaAs QDs were used for 1.3um-LD, PD etc.◄
InGaAlAs QDs were used for short-wavelength LD.
QD can be
Position controlled
3-5 devices can be transferred to
Si wafer
3-5 devices can be direct grown on Patterned Si
Band gap engineering
in thin film inorganic materials
1. Synthesis of Low-D Nanomaterials
2. Ultrafast Opto-Electronic Devices
3. Smart Human Interfaces
Low-D Nanostructured Materials & Devices Nonlinear nanomaterials Novel materials for nonlinear saturable absorbers & optical switches In situ synthesis of graphene on electronic and photonic devices Direct synthesis of nanomaterials onto integrated photonic devices High performance semiconductor materials & devices Novel materials for printed waveguides
Nanomaterial-Based Ultrafast Photonics Femtosecond fiber lasers Ultrafast nonlinear switches Optical logic gates Printed optical waveguides Fiber optic passive components High-speed optical signal management Novel modulation formats
Smart Contact Lenses Non-invasive health monitoring Diabetes monitoring via tear Biosensors with ultimate sensitivity & selectivity Microfluidic channels for reliable operation of the sensors Integrated chips for sensor control & data communication Remote power supply and body channel communication Tunable lenses
E
kx
ky
E
kx
ky
Nonlinear Saturable Absorption in Graphene
Inc
II
II
S
S
20
20
)3(
int0
0int0
int0
2)Im(3
~
/1
εχωαα
ααα
ααα
++=
−+
++
= Icn
nInnn 200
)3(
020 4)Re(3
εχ
+=+=
))()()(()( 3)3(2)2()1(0 ⋅⋅⋅+++= tttt EEEP χχχε
Absorption Refractive index
c
a
Deposited nickel layer
Ni atomC atom Grain boundaries
Amplified CW laser
t
CW laser after absorption
tWaveguide
Nickel on the waveguide
Interface Growth of Graphene in situ Synthesis of Graphene
Directly Grown CNTs onto Optical Fiber Substrate
Black Phosphorus-Based Field Effect Transistors
CVD-Grown Graphene
Graphene Growth on Ceramics (Metal-Free Growth)
Optical Deposition of Graphene Oxides
Ni (Catalyst)Graphene layer
(AFM data)Substrate
200 nm
Catalystremoval
Resultant graphene layer that does NOT require graphene transfer
Pulsed Output 10/90
Coupler EDFAIsolator
Isolator
PolarizationController
FiberFerrules
SWNTs or Graphene
Nanomaterial-Based Fiber Femtosecond Lasers
Nanomaterial-Based Ultrafast Nonlinear Kerr Switches
Four-Wave-Mixing in in situ Grown Graphene
Four-Wave-Mixing in Black Phosphorus
Integrated Optical Switches Functioned with Nanomaterials
Graphene onD-shaped fiber
Pump LD(λ: 1552.4 nm)
PC 2
High power EDFA
Band pass filter(3.2 nm )
PC 1
OSA
3 dB coupler
Analyzer (130 MHz~20 GHz) Band pass filter
(0.8 nm)
Signal LD (λ: 1559 nm)
EDFA
Nanomaterial-Based;Light Source
Photo DetectorTunable Filter
Optical ModulatorOptical Switch
Logic Gate
Electrical Layers
Optical Layers
Flexibility and transparency of materials and devices
Conventionally inefficient, painful glucose monitoring
Development of novel contact lens-
typed monitoring tool
Tear-based, painless, continuous monitoring
Highly efficient power management for sensor operation and data communication
Sensor head Microfluidic channels Secondary thin film battery Nano generator Integrated circuits
2014: Kick-off the Research 2016: Exhibition in Nano Korea
Individual devices and structure have been realized and displayed.
2017: Assembled Contact Lens Sensor Platform
Sensor head Microfluidic channels Secondary thin film battery Integrated circuits
2018: Newly Designed Contact Lens Sensor Platform
Sensor head Microfluidic
channels Chips for remote
power and data delivery
Transparent flexible devices (e.g. Omni-flex display devices)
Multi-purpose lenses
Health monitoring
Augmented reality (living info.)
Augmented reality (Navigation)
Artificial interfaceHigh-resolution display
on the contact lens
Future Researches
Hostmaterial
incorporating2D nanostructures
LP01-Y
∆φ(X-Y)
x
y
Pump
Probe
LP01-X
x
Polarizationrotatedprobe
Synthesis OF Low-Dimensional Nanomaterials and
Their Applications to Ultrafast Opto-Electronic Devices
2D/3D Imaging and Display Systems
• 2D or 3D images can be obtained with a single pixel sensor by proposed several imaging systems. • 2D/3D imaging system can be exploited to verify the imaging capability of prototype image sensors fabricated in laboratory level.• Any types of photo sensitive sensors to various wavelength (from UV to IR) can be tested by a designed imaging system.• Quality of primitive images obtained by the imaging system can be enhanced with various signal processing algorithms.
Conclusion
2 Dimensional Imaging system 3 Dimensional Imaging system
Optical Scanning Holography (OSH)
2 Dimensional image processing 3 Dimensional contents display
Chromatic confocal microscope : It is possible to use depth of focusgenerated in the microscope by using spectrometer
Single point confocal microscope + 2D linear stages → 3D imaging of thesamples
1cm
Cosine holo
50 100 150 200 250 300
50
100
150
200
250
300
Sine holo
50 100 150 200 250 300
50
100
150
200
250
300
Cosine holo Sine holo
Reconstruction
An optical wave is described by its amplitude and its phase. Theprincipal of holography is to generate an interference pattern so that theintensity captured in a given plane contains both amplitude and phaseinformation. It is then possible to reconstruct a 3D scene.
Optical scanning holography (OSH) is a technique to record complexhologram from a real object with a single pixel senor.
Chromatic Confocal Microscope
3D reconstruction result
200um
100um
SCAN
Single pixel imaging (mechanical scanner)
Compressive sensing does not require mechanical scanning.
Several measurement are taken for different binary pattern displayed by the SLM.
Single pixel imaging (Compressive sensing)
Emulation of plant’s vision by artificial photosynthesis
Artificial photosynthesis properties of TiO2 nanowire array was exploited to emulate plant’s vision
M: Number of binary pattern
N: Size of binary pattern
the images of Kalanchoe blossfeldiana captured by different sensors. Although the image takenby the proposed image scanning with the TiO2 nanowire array presents lower resolution ascompared to the images taken by the two different CCDs, the UV absorbing pattern is clearly seen.
Object Detection & Tracking
Stitching images Find features
Match features
Estimate homography matrix
Wrap images
Blend images
360 Degree Image Stitching
Multi-wavelength band fusion
Noise reduction filter
Eye tracking system
Motion capture based on IR markers
Set-up for Reconstruction of Holography
Reconstruction of Holography
In the reconstruction process, the hologram isilluminated by laser beam and this beam iscalled reconstruction beam. This beam is iden-tical to reference beam used in construction ofhologram.
The hologram acts a diffraction grating. Thisreconstruction beam will undergo phenomenonof diffraction during passage through the holo-gram. The reconstruction beam after passingthrough the hologram produces a real as well asvirtual image of the object.
Integral imaging display
Holographic display
Super High Barrier FilmsSiNx:H SiOx SiOxNy / SiOx
PECVD process
Silica sol dip coating
Thermal treatment
Chemical reaction formula
We fabricated high-performance inorganic SiNx/SiOxNy/SiOx barrier films
on PET substrates by using PECVD and simple dip coating.▲
SiOx
SiOxNy : 4.76 nm
SiNx
SiOx : 103.78 nm
328.51nm SiNx
PET (125㎛)
SiN x (PECVD 8min)SiOxNy
SiOx
Dip coating
( 1mm/s)
About
500nm
◀ The SiNx/SiOxNy/SiOx barrier
film had a transmittance of
90.37 % and the WVTR was
< 5.0×10−5 g/ m2 /day.
TEM images of SiNx/SiOxNy/SiOxSEM image of SiNx
300 400 500 600 700 800
40
60
80
100
Tran
smitt
ance
(%)
Wavelength (nm)
Bare PET : 88.79% SiNx on PET : 75.87% SiNx/SiOxNy on PET : 90.37%
Oxide Semiconductor and Polymer Hybrid
Nanomaterials for Soft Nano Electronics
• Intrinsic defects controlled ZnO and ZnO-graphene hybrid quantum dots: UV Photo-Excited White-Light Emission and Electro-Excited Purple-Blue Light Emitting Diodes
• Highly dispersible nanospring single-walled CNTs (NS SWVNTs): High dielectric PVDF and PDMS for energy harvesting with high contents of CNTs.
• SiNx/SiON/SiO2 super high barrier film: WVTR< 5x10-5 g/m2/day @1 dyad, <3x10-5 g/m2/day @2 dyad
• Coaxial PVDF-TrFE nanofiber(37μm)/metal wire(200 μm ): 0.3 [email protected] N & ca.0.9 [email protected]
Conclusion
(a) Inline magnetron sputter : Antireflection nano coating
(b) Inline magnetron sputter : TCO coater (ITO, WOx)
(c) UHV multi-sputter : Oxide semiconductor (ZnO, NiO, SnOx)
(d) Continuous Electrospinning : PVDF-TrFE/metal wire
(e) Glove box: thermal deposition for QD LED & OPV
(f) Glove box: PECVD for barrier film, slot die coating
ZnO-nanocarbon (Graphene, C60, CNTs), Carbon dots Nanospring Single Walled CNTs (NS SWCNTs)
Nano Energy Harvesting
• HR TEM image of ZnO-SWCNTs complex synthesized at various reaction time
• Chemical synthesis process for the buckled NS-CNTs
• The role of PVP and the schematic diagram
• Measured dielectric constant data of the P(VDF-TrFE) and NS-CNTs-PVP nanocomposite
a b
c d
e f
Bare PET SiNx on PET SiNx/SiOxNy/SiOx on PET10-5
10-4
10-3
10-2
10-1
100
101
< 5.0 x 10-5
1.4 x 10-2
WVT
R (g
/m2 /d
ay)
4.62
Continuously Electrospinning coating system on metal wire
◀
Power Supply
PVDF-TrFE
Solution
MotorCu wire
22 w/v% 24 w/v%
26 w/v% 28 w/v%
▲ PVDF-TrFE nanofibers on Cu wire was various concetration of PVDF-TrFE in solvent
20 40 60 80
Inte
nsity
(a.u
)
2 theta (2θ)10 20 30
Inte
nsity
(a.u
)
2 theta (2θ)
19.7 °
Cu (111)Cu (200)
Cu (220)
▲ XRD 2 θ spectra of PVDF-TrFE nanofibers on Cu wire at 28 w/v% PVDF-TrFE solution. Left 2 θ spectrum is range of 10 ° ~ 90 °, right one is enlarged at 10 ° ~ 30 ° range of left spectrum
200 μm 37 μm
1 cm 0 1 2 3 4 5 6-0.50
-0.25
0.00
0.25
0.50
Volta
ge (V
)
Time (s)
0.3N
-0.010
-0.005
0.000
0.005
0.010
Cur
rent
(µA)
0 1 2 3 4 5 6-0.5
0.0
0.5
1.0
Volta
ge (V
)
Time (s)
5.1N
-0.01
0.00
0.01
0.02
Cur
rent
(µA)2 x 2 cm2
0 1 2 3 4 5 6
-0.2
0.0
0.2
Volta
ge (V
)
Time (s)
-0.010
-0.005
0.000
0.005
0.0100.4N
Cur
rent
(µA)
0 1 2 3 4 5 6-0.5
0.0
0.5
1.0
1.5
2.0
Volta
ge (V
)
Time (s)
5.4N
-0.01
0.00
0.01
0.02
0.03
0.04
Cur
rent
(µA)
Φ = 1 cm 2 x 2 cm2◀ Cross sectional view of core-shell PVDF-TrFEnanofibers/metal wire
▶ Electrical properties of one and three core-shell PVDF-TrFE nanofiber /metal wire
Ligand exchange & Reduction
Carbonization
Amorphous domain
Crystalline domain
Citric acidCarbonization
Oleylamine
Synthesis of nano-carbon quantum dots (CQDs) by carbonization, ligand exchange, & reduction ▲
300 400 500 600 700200
300
400
500
600
700
390 nm
Emission Wavelength (nm)
Exci
tatio
n W
avel
engt
h (n
m)
477 nm
450 nm
QY :
6 %
300 400 500 600 700200
300
400
500
600
700
532 nm
450 nm
390 nm
442 nm
Emission Wavelength (nm)
Exci
tatio
n W
avel
engt
h (n
m)
QY :
30 %
2D PL mapping
Mixed dimensional semiconducting materials and their devices for next generation electronic/optoelectronic applications
Conclusion
Organic and Metal oxide semiconductors thin-films 0-dim Quantum dots
1-dim Nanowires 2-dim vander Walls (vdWs) nanosheets
New device platform technology with mixed-dimensional heterostructures
1-D nanowire 0-D QD
ex) PbS, CdSe ex) ZnO, InAS NW
ex) MoS2, WSe2, BP ex) InGaZnO
2-D nanosheet 3-D film
Mixed dimension
Pt
Au/Ti
Au/Ti
WSe2
Au/Ti
ZnO
BP
ass
0-D QD/3-D metal oxide hybrid
1-D Nanowire/2-D nanosheet hybrid
Equipment Electronic/Optoelectronic devices measurement system
Development of Organic and metal oxide semiconductors devices• High performance organic devices with solution process• Fundamental study on organic device reliability
• Organic/Metal oxide hybrid complementary inverter• Solution processed metal oxide thin film electronics
0-D PbS/3-D InGaZnO hybrid phototransistor for NIR imager• Gate tunable, highly sensitive, and easily integrated PbS sensitized IGZO hybrid
phototransistor for NIR detection
• PbS/IGZO device exhibits
photo detection capabilities
for NIR light up to 1400 nm.
• The photo-generated electrons
from the PbS sensitized layer
lead to significant negative
shifts of threshold voltage (Vth)
in the IGZO TFTs.
Metal shadow mask 1300 nm NIR image
z-axis(500μm)
x-axis(200μm)
VDD
VOUT
VIN1.5V
100 MΩ1300 nmLED source
• NIR (1300 nm) Imager
1-D Ag metal nanowire electrode
Ag NW Ag NW Ag NW
hv
hv
0
45ITO
PEDOT:PSS
P3HT:PC60BM
PET
PEDOT:PSS
P3HT:PC60BM
Ag NW
Al Al
Absorption density
-0.2 0.0 0.2 0.4 0.6
-10
-5
0 ITO Ag NW
Curre
nt d
ensi
ty (m
A/cm
2 )
Voltage (V)
P3HT:PC60BM
• High performance flexible organic solar cell
Light scattering and lighttrapping induced by the Agnanowire mesh: the enhancedlight absorption in the activelayer.
• IGZO TFT with Ag nanowire electrode based chemical/biological sensor
In Out
PDMS
Analyte
OH
OH
HO
HOOO
Glucose oxidase
OH
OH
OH
HO
OHO
b-D-glucose
OH
O
OH
Lactic acid
HO OHHydrogen peroxide
-1.0 -0.5 0.0 0.5 1.010-12
10-11
10-10
10-9
10-8
10-7
10-6
Ag NW mesh pH 3 pH 5 pH 7 pH 11
I DS (A
)
VGS (V)
VDS = 0.1 V
-20 -10 0 10 2010-1310-1210-1110-1010-910-810-710-610-510-410-3
Dark 1500 1400 1300 1000 700
VGS (V)
I DS (A
)
W/L = 1000 µm/ 50 µmVDS = 20 V
MixtureSingleOH
OH
OH
HO
OHO
b-D-glucose
+ O2OH
OH
HO
HOOO
D-glucono-1,5-lactone
+ HO OH
hydrogen peroxide
Sensors detect pH solution as well as biologically
relevant species such as H2O2, b-D-glucose, D-
glucono-1,5-Lactione, and Lactic acid in aqueous
media.
2D vdWs electronic/optoelectronic devices• Nonvolatile memory devices
Au top gateP(VDF-TrFE) (220 nm)
2D vDWs
GrapheneSource
GrapheneDrain
SiO2 (285 nm) / p+-Si
MoS2 and BP based ferroelectric memory transistor
Control gate (Au, 50 nm)20 nm
Al2O3 (35 nm)
Tunneling L (Al2O3, 5 nm)
Trapping L (BP, 6 nm)
Active L (BP, 7 nm)Glass substrate
0.56 nm
0.56 nm
4 nm4 nm
BP based charge injection memory transistor (flash memory)
• MoS2 image sensor
Au/Ti Au/Ti
MoS2Gr S/D Gr S/D
GreenLight
1Cm
1Cm
• 1D nanowire- 2D nanosheet heterostructures 1D ZnO – 2D BP diode and JFET 1D ZnO – 2D WSe2 photodiode
Device
LightSource(LED)
WSe2
• Organic/inorganic thin films and nanostructured materials based electronic/optoelectronic technologies have made great progress. In the thin film technology, organic/inorganic metal-oxide semiconductors are a promising alternative to amorphous or poly silicon.
• Low dimensional semiconducting materials such as colloidal QDs and van der Waals (2D vdWs) atomic crystals are an emerging class of new materials that can provide important resources for future electronics and materials sciences due to their unique physical properties.
• In this presentation, our group show various electronic and optoelectronic devices using 0D QD, 1D nanowire, 2D nanosheet, and 3D thin film semiconducting materials: Organic and metal oxide transistors, PbS QD sensitized InGaZnO phototransistor for NIR detection, Organic Solar cell and InGaZnO biosensor with 1D Ag nanowire electrode, and 2D vdWs semiconductor based electronic/optoelectronic devices (nonvolatile memory, image sensor, and 1D-2D heterostructures based devices). Our group will further develop a new device platform with mixed-dimensional heterostructures
• We are happy to work with co-workers in the world
Organic Semiconductor Engineering for
Printed & Soft-Electronics
Solution-Based Organic Electronics
Facile deposition of functional materials - 1D, 2D & 3D structure
<KIST die coating system>
Coating on Fiber
3D printing & Printing on 3D structure
Slot-die coating
Everywhere Electronics !
Large area- R2R
Multi function- Integration
Low cost- Solution-process
LightingPublic information
Wall Display
EntertainmentHealthcare/Sensor
Printed & Soft Electronics Vision Organic Semiconductors
Introduction 3-Dimensional self-organization of printed organic semiconductor
Fibriform, weavable organic transistor for E-Textile Split-second nanostructure control by intense pulsed light
Freestanding diamond plates (left) synthesized by KIST own multi-cathode direct currentplasma assisted CVD apparatus (right)
Carbon Science
• CVD synthesis of diamond: We developed KIST own apparatus, MCDC-PACVD which enables us to synthesis of freestanding diamond wafers (~1 mm thick) of 4”in diameter.
• Discovery of AA’ graphite: We discovered new crystalline structure of graphite which is metastable for AB graphite and shows nano-crystalline feature.• Define structures of CNTs: We defined structures of SWNTs and MWNTs to be a graphene helix and graphite helices, resulted from helical growth of a graphene
and graphited helices, respectively.• Graphene: We developed a new simple way to identify mono- and bi-layer graphene from ‘radial mode’ (appearing at 100-300 cm-1) on Raman spectrum (Monolayer
graphene is very seldom and nobody have shown evidence of the presence of monolayer graphene in micron size).
• We are happy to work with co-workers in the world.
Summary and comments
CVD synthesis of Diamond
~130 carat
Discovery of AA’ graphite
Evidence of GrapheneStructure of CNTs: Helix
Diamond shells (~ Φ 30 ㎛)
We explore the nature of carbon for next generation electronics
Φ 20 mm
DC plasma
~130 carats
HRTEM image revealing interface between diamond and graphene
Structure model of multi-wall carbon nanotubes
Structure model of single-wall carbon nanotubes
HRTEM images revealing the traces ofgraphite helix comprising MWNTs
Atomic structure of AA’ graphite assignedas orthorhombic
Energy landscape of graphite. AA’ stacking ofgraphene is metastable phase of graphite.
HRTEM image revealing mono- and bi-layer graphene where ends are curved (left) and lowenergy Raman radial mode (RM) signals (right).
Schematic models explaining radial mode (RM) of Eigen vectors
HRTEM images and Raman spectrum of plasmaseeded grown graphene
Atomic-resolution TEM morphology imagingoverlapped AA’ bilayer graphene.
Crystalline models of AA’ and AB graphiteand their simulated HRTEM images
(Lee et al., J. Phys. Chem. Lett. 2017)
(Lee et al., APL, 2013)
(Lee et al., Small, 2014)
(Lee et al., Scientific Reports, 2016)
(Lee et al., J. Phys. Chem. Lett. 2008)
(Lee et al., Diam. Relat. Mater., 2001)
(Lee et al., CVD, 2006)
Direct current plasma generated by KIST own equipment for synthesis of diamond
Memory Application based on Stochastic Devices: Random Number, Security, and Multi-Level Memory Cell
• Non-volatile memory application merges as alternative to conventional CMOS-based computing era. • Neuromorphic technologies and stochastic computing have attracted tremendous attention to overcome the limit of Moore’s law.• One of promising candidates is resistive change memory, which intrinsically has stochastic and multi-level characteristics applicable to those applications.• In this presentation, representative applications and results of ReRAM and ovonic threshold switch(OTS) devices are demonstrated – random number generator, synaptic device formachine learning, and physical unclonable function(PUF) for hardware security.
• Electrical investigation on the devices and computational works run complementarily such as device model simulation, output data processing, and novel algorithm development.• We are happy to work with co-workers in the world.
Random Number Generation (RNG) Security : Physical Unclonable Function (PUF)
0 20 40 60 80 100 120 140 160 180 200
0
1x10-8
2x10-8
3x10-8
4x10-8 LTP LTD
Nor
mal
ized
G
Normalized Pulses
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.510-910-810-710-610-510-410-310-2
Curre
nt (A
)
Voltage (V)
Measure Fitting
0 25 50 75 100
S/A = 5.5uAResponse = 60b
Cou
nt (A
.U)
Randomness (%)
w/o Mix Mix
0 25 50 75 100
Cou
nt (A
.U)
Uniqueness (%)
w/o Mix Mix
S/A = 5.5uAResponse = 60b
Non-volatile Resistive Change Memory
Multi-Level Cell Characteristic DC I-V Model Simulation
Stochastic Cycle-to-Cycle Characteristic Stochastic Cell-to-Cell CharacteristicSynaptic Behavior : Classification Test
0 20 40 60 80 100 120 1400
102030405060708090
100
Accuracy
Acc
urac
y [%
]
Epoch
Source : IBM X-Force Threat Intelligence Quaterly (2014)
Hardware Authentication : Challenge-Response Pair by PUF
CRP Generation Algorithm
Multi-Level Conductance (from nl904092h)
Training Result
Multi-layer Perceptron Neural Network
From IEEE TCAD.2018.2789723
110001110001001011
= 9/18
111001110000000011
= 8/18
Response of a Cortical Neuron (J.P. Hayes, DAC 2015) RNG Circuit with OTS (from S. Lee)
Vin
0.000 0.002 0.004-100
0
100
200
300
400
500
bin size : 50mV
Va [m
V]
Time [sec]
Va [mV]
Null
0.00 0.02 0.04
0
100
200
300
400
500
600
700
800
Va [m
V]
A
Va [mV] Null
-100 0 100 200 300 400 5000
500
1000
1500
2000
2500
3000
Null
Cou
nt
Va [mV]
raw w/o Null
Log-Normal Dist.
0
50
100
150
Cou
nt
Output of 10-pulse train (input)
Time [sec]
RNG Algorithm for a Single Pulse Input
Modified Random Number Distribution
Bit-Error-Rate Improvement Binning Sensitivity Effect Bit Streaming Comparison
Sampling Profile to Population Randomness Comparison Uniqueness Comparison
300 400 500 600 700 800 900
Inte
nsity
[a. u
.]
Wavelenght [nm]
Growth Principles
Synthesis of Hybrid Two-Dimensional
Nanomaterials in Layered Structures
Vision
Conclusion
Roadmap for Optical Integration
Developing Optical Logic Module
Ensure efficiency of photonics devices due to extremely low and high nonlinearity
of two-dimensional nanomaterials
For ultra low power and ultrafast operation, two-dimensional nanomaterials are needed.
Direct Synthesis of 2D Nanomaterials on Insulating Substrates
“Metal-free” & “Transfer-free” growth
“High-quality” & “Large-area” growth
Metal catalysts are not allowed for real semiconductor industry.
For facile fabrication, transfer is not good.
Direct synthesis of 2D materials on insulating substrates is essential
What we need is the intrinsic properties.
What we want is not flakes form.
Facile process is our way.
“Patterned” & “Layered” growth
Selective etching process has not been developed for hybrid two-dimensional materials in layered structures.
For special functions, new metamaterial structures are needed.
Patterned and layered growth is the answer.
Graphene
h-BN
Precursor supplying unit
Non-metal only
Precursor
ROM
Resistorcall
Translate
Control Unit
ALU
Execution
Resistor
StackedMemory
B
U
S
Chipset
IBM next generation microarchitecture
CPU Modularization
ROM
OpticalIntegration
ElectronicModule
동기화
E/O
Optical Computing Unit
OpticalDistributor
O/E
StackedMemory
B
U
S
Mounting the electronic modules on optical logic module
Chipset
Laser
E/O
E/O
O/E
O/E
Growing Devices and Functions2D
Universal 2D Growth ModelLow temp. η + Nx ~ Nx
High temp. η + Nx ~ η (𝜼𝜼 + 𝑵𝑵𝒙𝒙)𝟐𝟐
𝒅𝒅𝑵𝑵𝒙𝒙
𝒅𝒅𝒅𝒅=𝑪𝑪𝑹𝑹𝟐𝟐𝒑𝒑𝒂𝒂𝒅𝒅𝒅𝒅,𝒔𝒔𝑵𝑵𝟎𝟎
𝒒𝒒𝟎𝟎𝟐𝟐𝒑𝒑𝒅𝒅𝒑𝒑𝒂𝒂𝒅𝒅𝒅𝒅𝟐𝟐 −𝜷𝜷𝒑𝒑𝒎𝒎𝑹𝑹
𝒒𝒒𝟎𝟎𝒑𝒑𝒂𝒂𝒅𝒅𝒅𝒅𝑵𝑵𝟎𝟎(𝜼𝜼 + 𝑵𝑵𝒙𝒙)𝑵𝑵𝒙𝒙
𝟐𝟐
Relation
Growths based on Energy Barriers
Prediction and control of growth characteristics based on extensive energy barriers
h-BN
Gr
Guided Growths
Various templates for high-quality growth
Y. Gong, et al. Nature Commun. 2014, 5, 3193.
295 290 285 280
Inte
nsity
[a. u
.]
Binding Energy [eV]
C=C sp2 : 284.6
C-O : 286.5
96.1%
3.9%205 200 195 190 185 180
Inte
nsity
[a. u
.]
Binding Energy [eV]
h-BNB1s
415 410 405 400 395 390
Inte
nsity
[a. u
.]
Binding Energy [eV]
h-BNN1sFWHM : 1.64
FWHM : 1.70C1s
High-quality growth of hybrid h-BN//graphene
Electro-optic Modulators
Development of synthesis of hybrid 2D materials directly on photonics system
~4 nm thick h-BN film is need for photonics and electrical devices.
Mono- or Bi-layered h-BN film is essential for remote epitaxial growths.
Improving quality
Integration
Studying of E-O modulation
Layer number control
h-BN, graphene direct patterning
Achieved
OngoingElectrical signal
0 10 20 300
20
40
60
80
Thic
knes
s[nm
]
Time [min]
12
0
6
Height : 1.93 nm
nm
Layer number controlled h-BN (Quality: 96~100%)on various insulating and semiconducting substrates
h-BNSubstrate
Flexible White LEDs
We can grow 2D materials on fragile structures.
Facile processes were only used for our LEDs.
Surface properties can enhance PL intensity up to 2 orders.
20 nm thick GO bubbles
x100 x100
Starting material is graphene oxide (GO)bubbles (Dr. Kwon Seokjoon)
Applications of Interest
Graphene for band-gap engineering
h-BN for implementing intrinsic properties
(organic electronics, flexible electronics)
h-BN for flexible barrier films
Growing h-BNC for band-gap engineering
Synthesis of hyperbolic metamaterials
for vertical interconnects
Y. Gong, et al.
Nature Commun. 2014, 5, 3193.
Homogeneous
Domains
We are CVD synthesis guys.
We are synthesizing two-dimensional nanomaterials directly on insulating and semiconducting substrates
without the assistance of metal catalysts.
By using various diffusions and extensive energy barriers, high-quality and patterned 2D nanomaterials
in layered structures can be directly formed on those substrates.
h-BN is the only 2D insulating nanomaterial that guarantees the intrinsic properties of atomic thick 2D nanomaterials.
Our synthesis provides very important clues to the implementation of high-performance photonics and electronics devices.
We are interested in light controls for optical computing.
We believe that our unique synthesis provides a very important clue for implementing
optical integrated systems.
Our 1st goal is implementing E-O modulators on 3D photonics devices.
We want to provide well designed hybrid 2D layered nanostructures.
If you want to discuss with our group, do not hesitate.
E-mail: [email protected], Phone: 02-958-5328
Enables two-dimensionalnanomaterials
Quantum Random Number Generator
State-of-the-Art CMOS-APDs/SPADs
Advanced APD/SPAD Technologies for
LiDAR/Biomedical/Quantum Applications
CMOS-APD Technology
Conclusion
SPAD Technology
Applications – LiDAR, Bio, Quantum
Open for research collaboration!
We are looking for motivated postdocs and students! Contact: Dr. Myung-Jae Lee
(E-mail: [email protected] / Phone: 02-958-5309)
VR
IR
Geiger mode:SPAD
Linear mode:APD
Single-Photon Avalanche Diode
V
V
I
ConventionalAvalancheGeiger
Gain
VB
1VE + VB
Depletion RegionPhotodiode
EC
EV
Depletion RegionSPAD
EC
EV
VR
Cur
rent
Avalanche
APD SPAD
Photon
Off
OnQuench
Recharge
VB+VEVB
VB+VE
IA
Rq AvalanchePulse
Photon
Very high gain of Geiger-mode operation allows for
Single Photon Detection
Digital nature of SPAD output allows for
Time-of-Flight Detection&
Photon Counting
CMOS-Compatible Avalanche Photodetector
N-well
P+N+ N+STI
STI
P-substrate
P-well
P+ STI
P-well
P+STIHole
Diffusion
ElectronDiffusion
Penetration depth > 10 μm @ 850 nm
1~1.5 μm
Light Source
P+/N-well CMOS-APDs• Elimination of slow diffusion currents
from P-substrate Bandwidth enhancement (~GHz)
• Elimination of diffusion currents Reduced responsivity
Responsivity enhancement by high avalanche gain
[Impact ionization processes foravalanche multiplication]
• Responsivity [A/W]- Sufficient absorption region- Wider depletion width
• Photodetection Bandwidth- Photogenerated-carrier transit time - RC time constant- Parasitics
Important parameters
DepletionRegion
P N
E-field
V- V+
Popt
WD
hν
hν
hν
Electrondiffusion
HolediffusionDrift
s
D
AC
Wε
=
- Avalanche gain
- Inductive-peaking effect
Optimization and Improvement of Silicon APDs in Standard CMOS Technology [Invited Paper, Front Cover Article]
JSTQE’18
Equivalent Circuit Modeling Essential for CMOS-APD analysis and CMOS-Rx design
EDL’08
Optical Power Dependence Essential for variousoptical-interconnect applications
JSTQE’14
Junction– N+/P-well, (P+/N-well) World’s best gain-bandwidth (1820 GHz) OpEx’
10
Guard Ring– STI GR World’s best avalanche gain (2,500) EDL’
12
Active Area– 10×10 μm2 World’s best BW (7.6 GHz) TED’
13
Silicide Under Contacts Responsivity (40 %) &BW improvement (63 %)
EDL’16
Carrier-AccelerationTechnique BW improvement (40 %) PTL’
15
Spatially-Modulated APD (SM-APD) World’s best BW (12 GHz) PTL’
16
CMOS-Rx (SM-APD + TIA + EQ + LA) World’s best speed (12.5 Gb/s) OpEx’
14
CMOS-APD: Development, Full Characterization & Analysis, Optimization, and Performance Improvement Techniques
• Key features
‒ High responsivity over 0.3 A/W
‒ High bandwidth over 23 GHz@ 850 nm
‒ Based on standard CMOS
Photon time-of-flight with picosecond resolution
Object
Stopwatch
Speed of light ‘c’ = 3x108 m/sTime of flight (ToF) = 20 ns (20x10-9 s)
ToF2
Distance D = c x = 3 m
Direct Time-of-Flight (ToF) for LiDAR
We can get distancefrom object to receiver
From a pulse of light reflected by an object
3D Face Recognition
Space Navigation SystemTime-Resolved
Raman Spectroscopy
NASANASA
Apple
LeddarTech
Autonomous Vehicle
GE Healthcare
Time-of-Flight Positron Emission Tomography (TOF PET)
Fluorescence Lifetime Imaging Microscopy (FLIM)
AQUA
Near Infrared Imaging (NIRI)
Becker & Hickl GmbH
LiDAR(Light Detection and
Ranging)
BiomedicalApplications
Super-Resolution Microscopy
AQUA
U2OS cells stained with Alexa 647
Convallaria
20
-2-2
0
2
0
100
200
300
400
Phot
ons
O2HbHHb
Several world’s first & best SPADs– OpEx’15, IEDM’17, ISSCC’18, JSTQE’18, JSTQE’19, etc.– World’s best 3D IC SPAD (JSTQE’18) & SPAD-LiDAR Sensor (ISSCC’18)
P-epi
P-sub
3D connection
P+PW PW
NW NWN+N+
< 3 µm
Top
Bottom
3D IC SPAD
Max 430m
< 0.4% error
LiDAR Results
QuantumApplications
Dark Count Rate (DCR)Triggered by any generation
of free carriers instead of incident photons
Photon Detection Prob. (PDP)Probability of detection when a photon hits the
SPAD’s active area
6.8 kcps55.4 cps/μm2
31.8 % @600nm
Lowest DCR Highest efficiency Broadest spectrum
Best timing jitter
Timing JitterUncertainty of Δt between
a photon and a photon-generated avalanche pulse
Results- State-of-the-art
V. C. Coffey, Photonics Spectra, 2014
J. L
. O'B
rien,
Sci
ence
, 200
7
Uni
v. N
ice
Quantum Key DistributionOptical Quantum Computing
• High-performance CMOS-APDs can play an important role in optical-interconnect applicationsby enabling high-speed integrated optical receiver based on standard CMOS technology.
• High-performance linear-mode CMOS-APDs can also be exploited in various image applicationsrequiring high sensitivity and fast response.
• SPAD-based single-photon counting & time-of-flight sensors have received a great amount ofattention by scientific & industrial communities for a wide variety of applications. Strong impact on next-generation LiDAR & Bio & quantum applications with great scientific/economic/social potentials.
• Many SPAD-related researches/projects/collaborations are in progress. Ground breaking results are coming soon!
IDQ