A5007054242- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Ga2O3 and related materials
- Silicon Carbide Semiconductor Technologies
- Advanced Semiconductor Detectors and Materials
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Wireless Communication Techniques
- Wireless Communication Networks Research
- Semiconductor materials and interfaces
- Quantum Dots Synthesis And Properties
- Metal and Thin Film Mechanics
- Luminescence Properties of Advanced Materials
- Induction Heating and Inverter Technology
- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Quantum and electron transport phenomena
- Thin-Film Transistor Technologies
- Nanowire Synthesis and Applications
- Radio Frequency Integrated Circuit Design
- Cooperative Communication and Network Coding
- ZnO doping and properties
- Advanced MIMO Systems Optimization
- Chalcogenide Semiconductor Thin Films
- Electronic and Structural Properties of Oxides
Nihon Dempa Kogyo (Japan)
2010-2024
Tokushima Bunri University
2024
National Institute for Materials Science
2017
The University of Tokyo
1989-2011
Renesas Electronics (Japan)
2011
Tokyo University of Science
2005-2007
NTT (Japan)
1999-2006
Massachusetts Institute of Technology
2006
NTT (United States)
2002-2006
University of Tsukuba
2006
Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in industry silicon-based and currently faced with diminishing returns of performance versus cost investment. At material level, its high electric field strength electron mobility have already shown for frequency communications photonic applications. Advances on commercially viable large area substrates are now at the point where power conversion applications GaN cusp...
A GaInP(N)/GaAs( p) heterojunction bipolar transistor was fabricated by metalorganic chemical vapor deposition (MOCVD) for the first time. The common-emitter current gain exceeded 200 at a density around 10 A/cm2 and offset voltage as small 50 mV. Thermionic emission theory indicates that conduction-band discontinuity (ΔEc) GaInP/GaAs heterointerface is 30 meV room temperature this value more than 160 smaller 0.19–0.22 eV obtained C-V profile method. band-gap energy MOCVD-grown GaInP 60...
GaN super heterojunction field effect transistors (super HFET) based on the polarization junction concept are demonstrated for first time. The HFET has charges of 2-D electron gas and hole gas, respectively induced by positive negative at GaN/AlGaN/GaN heterointerfaces. Analogous to RESURF concept, these unintentionally doped compensate each other in off state condition enhance breakdown capability HFET. HFETs have been fabricated sapphire substrates electrical measurements show voltages...
Quantum-mechanically coupled well systems consisting of two GaAs wells 30 Å thick separated by an Al0.5Ga0.5As barrier whose thickness was varied from 12 to 40 have been grown metalorganic chemical vapor deposition. The photoluminescence spectra these indicated the splitting a degenerate single state into doublet state, symmetrical and antisymmetric state. location spectrum peak shoulders agreed with calculated energies using Dingle’s connection rule which assumes 85% conduction band offset...
High density two dimensional hole gas (2DHG) with a charge of 1.1×1013 cm-2 has been demonstrated for the first time in GaN/AlGaN heterostructures. The 2DHG is induced by negative polarization charges at interface. layer structures have designed based on theoretical simulation results to maximize density. heterostructures grown sapphire substrate metal organic chemical vapor deposition. Hall mobility 16 cm2 V-1 s-1 measured room temperature sheet resistance 35 kΩ/sq.
This paper proposes adaptive control of the number surviving symbol replica candidates, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> (m denotes stage index), based on minimum accumulated branch metric each in maximum-likelihood detection employing QR decomposition and M-algorithm (QRM-MLD) orthogonal frequency-division multiplexing with multiple-input-multiple-output (MIMO) multiplexing. In proposed algorithm, at mth (1lesmlesN...
Photoluminescence of AlxGa1−xAs/GaAs(x=0.54) single quantum wells grown by metal organic chemical vapor deposition has been investigated at both 75 and 4.2 K. AlGaAs/GaAs heterojunction abruptness was estimated to be within a few atomic layers comparing the peak energy well photoluminescence with values calculated on assumption that radiative transition takes place between n=1 electron subband heavy-hole in finite square potential At K, however, shifts several meV below energy, cause which...
Single-ion luminescence due to Mn2+ and donor-acceptor pair (Cu, Al), (Ag, Al) (Au, centered in hexagonal ZnS have been investigated at 75 K with a major focus on exciton structures the excitation spectra. Appearance of peaks spectra indicates that isoelectronic Mn center can bind free exciton. Such an binding is caused by hole-binding nature center. The A1 line accompanied oscillatory structure constant intervals 356 cm-1 indirect hot creation. Exciton DA varies from ambiguous distinctive...
The paper proposes an adaptive selection algorithm for surviving symbol replica candidates based on the maximum reliability in ML detection with QR decomposition and M-algorithm (QRM-MLD) OFCDM MIMO multiplexing. In proposed algorithm, newly-added at each stage are ranked from previous using multiple quadrant detection. Then, branch metrics calculated only limited number of high iterative loop increasing order accumulated candidate minimum one. Simulation results show that computational...
The activation energies of DX centers in AlGaAs doped with six different impurities (S, Se, Te, Si, Ge, and Sn) are measured by deep level transient spectroscopy. Remarkable trends established, which the group IV become shallower as mass number impurity increases, while those VI remain constant.
A comprehensive overview of the novel high voltage GaN field effect transistors (FETs) based on Polarization Superjunction (PSJ) concept, and a cost-effective approach towards manufacturing these performance devices are presented. Current challenges impeding wider adoption power switching in applications, latest results scaled-up PSJ-FETs from POWDEC KK, also discussed. The article presents hard-switching characteristics 400–800 V boost converter, constructed using PSJ-FET grown sapphire...
Current–voltage characteristics of GaAs/AlxGa1−xAs /GaAs heterobarriers grown by metalorganic chemical vapor deposition were investigated for x from 0.32 to 0.46. Calculation the current, which included just two components—a tunneling component and a thermionic component—agreed well with experimental results. The effective mass used is same as Γ point when 0.32; this value allows calculated results fit data. becomes much larger than increases. This fact suggests that other band edge X...
An AlN/GaN insulated gate heterostructure FET is presented. n+GaN channel placed on a thick Al0.15Ga0.85N layer and covered by 4 nm AlN insulator layer. The has threshold voltage of near 0 V. A Gm 220 mS/mm for 1.4 µm length was obtained.
This paper presents experimental results on real-time packet transmission of greater than 1 Gb/s using 4-by-4 multiple-input-multiple-output (MIMO) multiplexing and maximum-likelihood detection (MLD)-based signal with a decreased level computational complexity in orthogonal frequency-division (OFDM) radio access. We apply our previous algorithm called adaptive selection surviving symbol replica candidates (ASESS) based the maximum reliability MLD employing QR decomposition M-algorithm...
This paper proposes likelihood function generation of complexity-reduced maximum detection with QR decomposition and M-algorithm (QRM-MLD) suitable for soft-decision turbo decoding investigates the throughput performance using QRM-MLD proposed in multipath Rayleigh fading channels orthogonal frequency code division multiplexing (OFCDM) multiple-input multiple-output (MIMO) multiplexing. Simulation results show that by scheme following 4-by-4 MIMO multiplexing, required average received...
An attempt at a qualitative understanding of the luminescence saturation mechanisms ZnS: Cu, Al phosphor has been made by studying exicitation current-density dependences efficiencies and decays several activator concentrations, temperatures accelerating voltages. The behavior is independent Cu concentrations in region >10 -4 g·atom/mol-ZnS. Neither temperature nor voltage affects saturation. Nonradiative deactivation luminescent centers occurs early stages decay. Auger recombination...
A GaN Schottky diode with a lateral structure for microwave power rectification was developed on semi-insulating silicon carbide substrate. Device evaluation showed that the turn-on voltage around 0.8 V. The on-resistance of one finger 25.6 Ω, breakdown voltages those field plate reached 93 V, wafer doping level 4.0 ×1016 cm-3. forward and reverse characteristics became stabilized after surface etching. RF measurement at 2.45 GHz capacitance about 0.29 pF bias 0 value is satisfactorily small...
Mechanisms of concentration quenching green-Cu luminescence in hexagonal ZnS:Cu,Al under cathode-ray excitation are investigated. The observed dependence the intensity is explained well by a model assuming complete pairing donors and acceptors. Interstitial Cu+ centers formed during synthesis, their determined thermodynamic equilibrium with other defects at firing temperature. They act as recombination for free carriers provide dominant nonradiative path energy when Cu larger than that Al....
Abstract This paper reports the developments of evaluation methods on epitaxially grown superlattices by means sputterassisted Auger electron spectroscopy (AES), scanning microscopy (SEM) and transmission (TEM). AlGaAs/GaAs semiconductor superlattics were metal–organic chemical vapour deposition (MOCVD). The layer thickness ranged from a few to ten nanometers. Firstly, depth profiling tried using: (1) differential pumping‐type ion gun instead static pressure type reduce oxygen adsorbates...
AlAs/GaAs monolayer scale superlattices were grown by atmospheric pressure-MOCVD and the layer structure was observed with a transmission electron microscope (TEM). Clear stripes high contrast in TEM lattice image indicated ultra-abrupt hetero-interfaces. The diffraction pattern of showed that hetero-interface nearly free island-like even such very short period superlattice as (AlAs) 5 -(GaAs) 2 .
Continuous-wave operation at room temperature was demonstrated in a GaInN/GaN multiquantum well (MQW) laser grown by metal organic chemical vapour deposition (MOCVD) using horizontal reactor. The structure on (0001) c-plane sapphire substrate. A 1 mm long cavity with 4 µm wide ridge stripe formed cleaving along the (11-20) plane of epitaxial layers. Stimulated emission observed wavelength 411 nm threshold current density 11.7 kA/cm2.
We report the first observation of negative differential resistance (NDR) at room temperature in InAs/GaSb barrier heterostructures, where conduction band InAs lies below GaSb valence band.
We propose a novel AlN/GaN insulated gate heterostructure field effect transistor (FET) with modulation doping. The vertical structure of the FET was AlN(1)/AlGaN(2)/InGaN(3)/AlGaN(4)/AlGaN(5)/GaN(substrate)(6). typical widths insulator (1) and channel (3) are 4 5 nm, respectively. Charge control in simulated one dimension by solving Poisson Schrödinger equations self-consistently. dependence transconductance (Gm) cutoff frequency (fT) on voltage (Vgs) obtained, then optimum determined....
InAs/GaAs single quantum well structures have been grown by metalorganic chemical vapor deposition. The wells are 1.03, 1.3, and 1.7 InAs monolayers thick. 4 K photoluminescence spectra exhibit strong narrow peaks, their energy decreasing smoothly with increasing thickness. noninteger value is interpreted on the model that interface macroscopically flat but has valleys hills lateral extent smaller than excitons. effective position determined relative extent.