A5025125075- Ga2O3 and related materials
- ZnO doping and properties
- Semiconductor Lasers and Optical Devices
- Advanced Photocatalysis Techniques
- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
- Semiconductor materials and devices
- GaN-based semiconductor devices and materials
- Electronic and Structural Properties of Oxides
- Optical Network Technologies
- Semiconductor materials and interfaces
- Advanced Photonic Communication Systems
- Advanced Semiconductor Detectors and Materials
- Integrated Circuits and Semiconductor Failure Analysis
- Laser Design and Applications
- Advanced Optical Network Technologies
- Gas Sensing Nanomaterials and Sensors
- Luminescence Properties of Advanced Materials
- solar cell performance optimization
- Transition Metal Oxide Nanomaterials
- Advanced Optical Sensing Technologies
- Magnesium Oxide Properties and Applications
- CO2 Reduction Techniques and Catalysts
- Chalcogenide Semiconductor Thin Films
- Solid State Laser Technologies
Tokyo University of Agriculture and Technology
2016-2022
National Institute of Information and Communications Technology
2016-2022
Novel (United States)
2019
Kogakuin University
2018
Fujitsu (Japan)
1984-2002
Tohoku University
1974-1982
We report a demonstration of single-crystal gallium oxide (Ga2O3) metal-semiconductor field-effect transistors (MESFETs). A Sn-doped Ga2O3 layer was grown on semi-insulating β-Ga2O3 (010) substrate by molecular-beam epitaxy. fabricated circular MESFET with gate length 4 μm and source–drain spacing 20 μm. The device showed an ideal transistor action represented the drain current modulation due to voltage (VGS) swing. complete pinch-off characteristic also obtained for VGS < −20 V,...
This is a review article on the current status and future prospects of research development gallium oxide (Ga2O3) power devices. Ga2O3 possesses excellent material properties, in particular for device applications. It also attractive from an industrial viewpoint since large-size, high-quality wafers can be manufactured single-crystal bulk synthesized by melt–growth methods. These two features have drawn much attention to as new wide bandgap semiconductor following SiC GaN. In this review, we...
Abstract β-Ga 2 O 3 bulk crystals were grown by the edge-defined film-fed growth (EFG) process and floating zone process. Semiconductor substrates containing no twin boundaries with sizes up to 4 in. in diameter fabricated. It was found that Si main residual impurity EFG-grown effective donor concentration ( N d − a ) of unintentionally doped governed concentration. Intentional n-type doping shown be possible. An etch pit observation revealed dislocation density on order 10 cm −3 . for...
Single-crystal gallium oxide (Ga2O3) metal-oxide-semiconductor field-effect transistors were fabricated on a semi-insulating β-Ga2O3 (010) substrate. A Sn-doped n-Ga2O3 channel layer was grown by molecular-beam epitaxy. Si-ion implantation doping performed to source and drain electrode regions for obtaining low-resistance ohmic contacts. An Al2O3 gate dielectric film formed atomic deposition passivated the device surface significantly reduced leakage. The with length of 2 μm showed effective...
N-type Ga2O3 homoepitaxial thick films were grown on β-Ga2O3(010) substrates by ozone molecular beam epitaxy. The epitaxial growth rate was increased more than ten times changing from the (100) plane to (010) plane. carrier concentration of layers could be varied within range 1016–1019 cm-3 Sn doping concentration. Platinum Schottky barrier diodes (SBDs) 1.4-µm-thick β-Ga2O3 demonstrated for first time. SBDs exhibited a reverse breakdown voltage 100 V, an on-resistance 2 mΩ cm2, and forward...
Ga2O3 field-plated Schottky barrier diodes (FP-SBDs) were fabricated on a Si-doped n−-Ga2O3 drift layer grown by halide vapor phase epitaxy Sn-doped n+-Ga2O3 (001) substrate. The specific on-resistance of the FP-SBD was estimated to be 5.1 mΩ·cm2. Successful field-plate engineering resulted in high breakdown voltage 1076 V. A larger-than-expected effective height 1.46 eV, which extracted from temperature-dependent current–voltage characteristics, could caused effect fluorine atoms delivered...
Gallium oxide (Ga 2 O 3 ) is a strong contender for power electronic devices. The material possesses excellent properties such as large bandgap of 4.7–4.9 eV high breakdown field 8 MV cm −1 . Low cost, volume production single‐crystal β‐Ga substrates can be realized by melt‐growth methods commonly adopted in the industry. High‐quality n‐type Ga epitaxial thin films with controllable carrier densities were obtained ozone molecular beam epitaxy (MBE). We fabricated metal‐semiconductor...
Depletion-mode field-plated Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> metal-oxide-semiconductor field-effect transistors were demonstrated for the first time. Substantial enhancement in breakdown voltage was achieved with a gate-connected field plate. The device channels, formed by selective-area Si ion implantation doping of an undoped epilayer, electrically isolated highly...
We fabricated gallium oxide (Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) Schottky barrier diodes using β-Ga single-crystal substrates produced by the floating-zone method. The crystal quality of was excellent; X-ray diffraction rocking curve peak had a full width at half-maximum 32 arcsec, and etch pit density less than 1×10 <sup...
Thick high-purity β-Ga2O3 layers of high crystalline quality were grown homoepitaxially by halide vapor phase epitaxy (HVPE) using gaseous GaCl and O2 on (001) substrates prepared edge-defined film-fed growth. The surface morphology structural the layer improved with increasing growth temperature. X-ray diffraction ω-rocking curves for (002) (400) reflections at 1000 °C had small full widths half maximum. Secondary ion mass spectrometry electrical characteristics revealed that low effective...
We investigated the temperature-dependent electrical properties of Pt/Ga2O3 Schottky barrier diodes (SBDs) fabricated on n–-Ga2O3 drift layers grown single-crystal n+-Ga2O3 (001) substrates by halide vapor phase epitaxy. In an operating temperature range from 21 °C to 200 °C, contact exhibited a zero-bias height 1.09–1.15 eV with constant near-unity ideality factor. The current–voltage characteristics SBDs were well-modeled thermionic emission in forward regime and field reverse over entire range.
We developed a donor doping technique for β-Ga2O3 by using Si-ion (Si+) implantation. For the implanted Ga2O3 substrates with Si+=1×1019–5×1019 cm-3, high activation efficiency of above 60% was obtained after annealing in nitrogen gas atmosphere at relatively low temperature 900–1000 °C. Annealed Ti/Au electrodes fabricated on layers showed ohmic behavior. The Si+=5×1019 cm-3 lowest specific contact resistance and resistivity this work 4.6×10-6 Ω·cm2 1.4 mΩ·cm, respectively.
We developed β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> trench MOS-type Schottky barrier diodes (MOSSBDs) for the first time. A Sidoped Ga layer was grown via halide vapor phase epitaxy on a single-crystal Sn-doped (001) substrate. The structure fabricated using dry etching and photolithography. HfO film used as dielectric of MOS structure. specific on-resistances (RON,SP)...
The band alignment of Al2O3/n-Ga2O3 was investigated by x-ray photoelectron spectroscopy (XPS). With a gap 6.8 ± 0.2 eV measured for Al2O3, the conduction and valence offsets at interface were estimated to be 1.5 0.7 eV, respectively. offset also obtained from tunneling current in (2¯01) metal-oxide-semiconductor (MOS) diodes using Fowler-Nordheim model. electrically extracted value good agreement with XPS data. Furthermore, MOS exhibited small capacitance-voltage hysteresis loops,...
We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared farinfrared active modes. apply our $\beta$-Ga$_2$O$_3$ single crystal samples. Surfaces cut under different angles from bulk crystal, (010) ($\bar{2}$01), are investigated by generalized spectroscopic ellipsometry within spectral regions. determine frequency dependence 4 independent Cartesian elements matching large sets...
Deep acceptor doping of β-Ga2O3 with Mg and N was demonstrated by implantation the impurity ions into n-type bulk substrates. Systematic physical electrical characterizations were performed to demonstrate recovery implantation-damaged crystals activation dopant atoms thermal annealing at 1000–1200 °C in an N2 atmosphere. found exhibit much lower diffusivity than Mg, thus enabling use higher temperatures maximize efficiency without significantly altering profile. Consequently,...
A single longitudinal mode (SLM) operating condition for phase-adjusted (PA) DFB lasers has been made clear both experimentally and theoretically. As expected, we got a high SLM operation yield of 80 percent in moderate coupled case up to light output power 10 mW. However, the strongly cases, two-mode with TE0 TE + 1 occurred frequently. To explain optimize PA-DFB laser structure, have developed theory. Taking spatial hole burning along axis into account, succeeded explaining behavior. From...
Enhancement-mode β-Ga2O3 metal–oxide–semiconductor field-effect transistors with low series resistance were achieved by Si-ion implantation doping of the source/drain contacts and access regions. An unintentionally doped Ga2O3 channel background carrier concentration that was fully depleted at a gate bias 0 V gave rise to positive threshold voltage without additional constraints on dimensions or device architecture. Transistors length 4 µm delivered maximum drain current density (IDS) 1.4...
A β-(AlxGa1−x)2O3:Si/Ga2O3 modulation-doped structure was fabricated by direct β-(AlxGa1−x)2O3 epitaxial growth on a (010) β-Ga2O3 substrate. Si the order of 1018 cm−3 from adsorbed contaminants substrate surface doped into layer. The heterojunction interface exhibited confined sheet carrier density ∼3 × 1012 cm−2, which is same as that AlGaAs/GaAs. successful modulation doping for β-(AlxGa1−x)2O3/Ga2O3 heterostructure encourages development β-Ga2O3-based field-effect transistors.
Abstract The electron mobility in depletion-mode lateral β-Ga 2 O 3 (010) metal–oxide–semiconductor field-effect transistors (MOSFETs) with an n-channel formed by Si-ion (Si + ) implantation doping was extracted using low-field electrical measurements on FET structures. An undoped Ga buffer layer protected the channel against charge compensation suppressing outdiffusion of deep Fe acceptors from semi-insulating substrate. molecular beam epitaxy growth temperature identified as a key process...
Abstract We have structurally evaluated β-Ga 2 O 3 crystals grown by edge-defined film-fed growth process using etch pitting, focused ion beam scanning microscopy, transmission electron and related techniques. found three types of defects: arrays edge dislocations corresponding to pit on <?CDATA $(\bar{2}01)$?> -oriented wafers, platelike nanopipes pits revealed the (010)-oriented twins including twin lamellae.