A5100420191- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- ZnO doping and properties
- Semiconductor materials and devices
- Metal and Thin Film Mechanics
- Silicon Carbide Semiconductor Technologies
- Semiconductor materials and interfaces
- Semiconductor Quantum Structures and Devices
- Black Holes and Theoretical Physics
- Advancements in Semiconductor Devices and Circuit Design
- Quantum Chromodynamics and Particle Interactions
- Gas Sensing Nanomaterials and Sensors
- Acoustic Wave Resonator Technologies
- Nanowire Synthesis and Applications
- Theoretical and Computational Physics
- Nonlinear Waves and Solitons
- Photocathodes and Microchannel Plates
- Material Dynamics and Properties
- Cosmology and Gravitation Theories
- Advanced Thermodynamics and Statistical Mechanics
- Scientific Research and Discoveries
- Radio Frequency Integrated Circuit Design
- Optical Coatings and Gratings
- Complex Network Analysis Techniques
- Ferroelectric and Negative Capacitance Devices
Samsung (South Korea)
2011-2022
University of British Columbia
2016-2017
Massachusetts Institute of Technology
2014-2015
Korea Advanced Institute of Science and Technology
2013
Kyungpook National University
2001-2012
Sungkyunkwan University
2006
In recent years, artificial intelligence (AI) technology has proliferated rapidly and widely into application areas such as speech recognition, health care, autonomous driving. To increase the capabilities of AI more powerful systems are needed to process a larger amount data. This requirement made domain-specific accelerators, GPUs TPUs, popular; they can provide orders magnitude higher performance than state-of-the-art CPUs. However, these accelerators only operate at their peak when get...
We analyze the constraints imposed by unitarity and crossing symmetry on four-point function of stress-tensor multiplet $$ \mathcal{N}=8 superconformal field theories in three dimensions. first derive blocks analyzing Ward identity. Our results imply that OPE primary operator with itself must have parity symmetry. then relations between equations, we find these equations are mostly redundant. implement independent numerically bounds coefficients dimensions as a central charge. To make...
We use the superconformal bootstrap to derive exact relations between OPE coefficients in three-dimensional field theories with $$ \mathcal{N}\ge 4 supersymmetry. These follow from a consistent truncation of crossing symmetry equations that is associated cohomology certain supercharge. In \mathcal{N}=4 SCFTs, non-trivial classes are one-to-one correspondence half-BPS operators, provided these operators restricted lie on line. The we find powerful enough allow us determine an infinite number...
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> High-quality InGaN–GaN film was grown on a cone-shape-patterned sapphire substrate (CSPSS) by using metal–oganic chemical vapor deposition. The growth mode of GaN CSPSS similar to that the epitaxial lateral overgrowth (ELOG), because growth, in initial stage, proceeds only flat basal and there is no preferential plane cone region. An analysis X-ray diffraction showed shorter lattice constant...
Ni–AlGaN/GaN Schottky barrier diodes (SBDs) with lateral geometry were fabricated on sapphire substrates. At 300 K, devices 500-μm-diameter contacts exhibited breakdown voltage (VB) of 765 V, forward current (IF) 0.065 A at 1.5 and specific on-resistance (Ron) 81.3 mΩ cm2, producing a figure-of-merit (VB2/Ron) ∼7.2 MW cm−2. Measured in multifinger patterns, the same parameters 420 3.2 A, 4.6 38.4 cm−2, respectively, K. With increase measurement temperature from to 450 SBDs dimensions...
The carrier transport mechanism of CF4 plasma-treated AlGaN/GaN Schottky barrier diodes (SBDs) under reverse bias is investigated. leakage current reduced by ∼2 orders magnitude after the plasma treatment, but increases exponentially with increasing temperature, indicating that a thermally activated involved. Based on activation energy estimated from temperature-dependent current-voltage characteristics and emission height extracted Frenkel-Poole model, it suggested dominant in treated SBDs...
We have demonstrated the lateral multifinger-type Schottky barrier diode (SBD) with bonding pad over active structure fabricated on AlGaN/GaN heterostructure prepared sapphire substrate. The GaN-SBD size of 9 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm mm}^{2}$</tex></formula> exhibited excellent device characteristics such as forward current 4.5 A at 1.5 V, leakage 6...
An AlGaN/GaN-based Ω-shaped nanowire fin-shaped FET (FinFET) with a fin width of 50 nm was fabricated using tetramethylammonium hydroxide (TMAH)-based lateral wet etching. atomic layer deposited (ALD) HfO2 side-wall served as the etching mask. ALD Al2O3 and TiN layers were used gate dielectric metal, respectively. The structure fully depletes active body almost completely separates depleted from underlying thick GaN buffer layer, resulting in superior device performance. top-down processing...
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> To improve the external quantum efficiency, we have proposed a new method utilizing surface roughening of vertical-type light-emitting diodes (VT-LEDs) fabricated on hemispherical patterned sapphire substrate by using laser lift-off technique. The advantages this are simple and reproducible in transferring well-defined patterns into GaN layer. VT-LED with concavely showed nearly twofold increase...
SiO2Al2O3 double dielectric stack layer was deposited on the surface of GaN-based light-emitting diode (LED). The enhances both electrical characteristics and optical output power LED because first Al2O3 plays a role effectively passivating p-GaN second lower index SiO2 increases critical angle light emitted from surface. In addition, effect Fresnel reflection is also responsible for enhancement in passivated LED. leakage current with -3.46 × 10-11 A at -5 V, least two three orders magnitude...
This study examines the influence of growth mode on defect formation and strain relaxation in GaN thin films grown cone-shaped patterned sapphire (CSPS) substrates by metal-organic chemical vapor deposition. A dramatic reduction luminescence dark spot density a red-shifted excitonic emission were found for CSPS compared to planar substrates. The results also show that both crystal quality optical properties are improved with strong spatial correlation between spots local structural due...
A <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{SiO}_{2}/\hbox{Al}_{2}\hbox{O}_{3}$</tex></formula> double dielectric stack layer was deposited on the surface of a GaN-based light-emitting diode (LED). The increases optical output power LED because first Notation="TeX">$ \hbox{Al}_{2}\hbox{O}_{3}$</tex></formula> plays role as an effective passivation and second...
A crack-free GaN film grown on 4-inch Si (111) substrate is proposed using two-step growth methods simply controlled by both III/V ratio and pressure. Two-step process found to be effective in compensating the strong tensile stress layer substrate. The high-resolution X-ray diffraction (XRD) rocking curves of (002) (102) planes for epitaxial with method are 317 432 arcsec, while corresponding values reference sample without 550 1207 respectively. reduced threading dislocation obtained ~2 ×...
We report on a metal–insulator–semiconductor AlGaN/GaN heterostructure field-effect transistor (MIS-HFET) using Al2O3 simultaneously for channel passivation layer and as gate insulator which was deposited by plasma enhanced atomic deposition(PE-ALD). Capacitance–voltage measurements show successful surface the dielectric layer. For length 1.2 μm with 15 source-to-drain spacing maximum drain current 1.22 A/mm, transconductance 166 mS/mm leakage 4 nA/mm at Vgs = −20 V is least three orders of...
A crack-free AlGaN/GaN heterostrucure is grown on 4-in Si (111) substrate with AlSiC precoverage layer. Covering the surface layer, until growth of AlN wetting buffer found to be effective in compensating strong tensile stress GaN layer substrate. The metal-oxide-semiconductor field-effect transistor, fabricated this heterostructure, exhibits excellent normally-off characteristics threshold voltage 7.2 V, maximum drain current 120 mA/mm, ON/OFF ratio <formula formulatype="inline"...
Multifinger lateral-type AlGaN/GaN Schottky barrier diode (SBD) with bonding pad over active (BPOA) structure was fabricated and exhibited excellent device performances, such as forward current of 6 A at 1.5 V, leakage 16 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{A}$</tex></formula> Notation="TeX">$-$ </tex></formula> 600 reverse-recovery time Notation="TeX">$(T_{\rm...
For holographic CFT states near the vacuum, entanglement entropies for spatial subsystems can be expressed perturbatively as an expansion in one-point functions of local operators dual to light bulk fields. Using connection between quantum Fisher information and canonical energy spacetimes, we describe a general formula this up second-order functions, arbitrary ball-shaped region, extending first-order result given by first law. two-dimensional CFTs, use derive completely explicit...
We study CFT data of 3-dimensional superconformal field theories (SCFTs) arising from wrapped two M5-branes on closed hyperbolic 3-manifolds. Via so-called 3d/3d correspondence, central charges these SCFTs are related to a SL(2) Chern-Simons (CS) invariant the After developing state-integral model for invariant, we numerically evaluate several 3-manifolds with small volume. The computation suggests that M5-brane systems give infinitely many discrete charges.
A high-performance normally off GaN-based MOSFET was fabricated. The buffer layer of the grown by varying growth temperature to control size nucleation sites which results in an extremely high resistance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(> \hbox{10}^{12}\ \Omega/\hbox{sq})$</tex></formula> . fabricated small-area exhibited excellent device characteristics, such as a threshold...
The effects of isoelectronic Al doping into epitaxial GaN films grown by metal organic chemical vapor deposition on sapphire substrates were investigated. It was found, based the measured electron mobility and x-ray analysis, that there is a limiting point incorporation in improving crystal quality. undoped film 178 cm2/V s value greatly increased to 524 small amount (up 0.45% concentration) layer. A further increase concentration resulted degradation mobility, which decreased 138 when...
This study investigates optical properties and carrier dynamics of InGaN-based light-emitting diodes grown on cone-shaped patterned sapphire (CSPS) planar substrates. Edge-type threading dislocations were dramatically reduced in InGaN multiple quantum wells (MQWs) CSPS substrates compared to the case We observed a smaller Stokes shift enhanced efficiency for From time-resolved analysis, we found that non-radiative (radiative) recombination rate MQWs is lower (higher) than substrates, which...
Abstract Strong gravitational lenses are a singular probe of the Universe’s small-scale structure—they sensitive to effects low-mass (<10 10 M ⊙ ) halos even without luminous counterpart. Recent strong-lensing analyses dark matter structure rely on simulation-based inference (SBI). Modern SBI methods, which leverage neural networks as density estimators, have shown promise in extracting halo-population signal. However, it is unclear whether constraints from these models limited by...
We report the drastic enhancement pattern of Shubnikov–de Haas (SdH) oscillations observed in an AlGaN/GaN heterostructure by microwave modulation. The dependence SdH on power and temperature is investigated. underlying mechanism attributed to effect carrier heating. This technique helps study transport properties two-dimensional electrons many wide-band-gap heterostructures, which moderate mobilities heavier electron effective mass (rapidly damping amplitudes) are frequently encountered. In...