A5062647657- ZnO doping and properties
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Quantum Dots Synthesis And Properties
- Semiconductor materials and devices
- Advanced Photocatalysis Techniques
- Chalcogenide Semiconductor Thin Films
- GaN-based semiconductor devices and materials
- Thin-Film Transistor Technologies
- Gas Sensing Nanomaterials and Sensors
- Electronic and Structural Properties of Oxides
- Advanced Semiconductor Detectors and Materials
- Copper-based nanomaterials and applications
- Semiconductor materials and interfaces
- Organic Electronics and Photovoltaics
- Magnesium Oxide Properties and Applications
- Organic Light-Emitting Diodes Research
- Silicon and Solar Cell Technologies
- Transition Metal Oxide Nanomaterials
- Semiconductor Lasers and Optical Devices
- Perovskite Materials and Applications
- Photonic and Optical Devices
- Silicon Nanostructures and Photoluminescence
- Nanowire Synthesis and Applications
- Molecular Junctions and Nanostructures
Kyoto University
2015-2024
Kyoto University of Education
2022
Wakayama University
2022
Kogakuin University
2021
Tokyo Metropolitan Industrial Technology Research Institute
2021
Kyoto Katsura Hospital
2007-2019
National Institute of Polar Research
2019
Graduate School USA
2011-2019
Saga University
2018
National Institute for Materials Science
2018
Structural analysis was performed on a purple laser diode composed of In0.20Ga0.80N (3 nm)/ In0.05Ga0.95N (6 nm) multiple quantum wells, by employing transmission electron microscopy and energy-dispersive x-ray microanalysis, both which are assessed from the cross-sectional direction. It found that contrast light shade in well layers corresponds to difference In composition. The main radiative recombination attributed excitons localized at deep traps probably originate In-rich region wells...
(201)-oriented β-Ga2O3 thin films were grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. In-plane X-ray diffraction measurements revealed the inclusion of α-Ga2O3 and rotational domains. However, film under optimized growth conditions exhibited a sharp absorption edge at around 5.0 eV, which is in deep-ultraviolet region. An ohmic-type metal–semiconductor–metal photodetector showed high resistance 6 GΩ with small dark current 1.2 nA 10 V bias voltage. Under 254...
Dynamical behavior of radiative recombination has been assessed in the ${\mathrm{In}}_{0.20}$${\mathrm{Ga}}_{0.80}$N (2.5 nm)/ ${\mathrm{In}}_{0.05}$${\mathrm{Ga}}_{0.95}$N (6.0 nm) multiple-quantum-well structure by means transmittance, electroreflectance (ER), photoluminescence excitation (PLE), and time-resolved (TRPL) spectroscopy. The PL at 20 K was mainly composed two emission bands whose peaks are located 2.920 eV 3.155 eV. Although peak weak under low photoexcitation, it grew...
Ga2O3 thin films of the α-phase, that is, corundum structure (in trigonal system), have been epitaxially obtained on sapphire (α-Al2O3) substrates, in contrast to strong tendency assume a heterogeneous crystal structure, β-gallia monoclinic system) sapphire. This result is advantageous for high-quality and due growth by mist chemical vapor deposition (CVD) at low temperatures 430–470 °C. The α-Ga2O3 narrow full-widths half maximum (FWHMs) their X-ray diffraction rocking curves, example,...
A vertical-type Schottky photodetector based on a (100)-oriented β-Ga2O3 substrate has been fabricated with simple processes of thermal annealing and vacuum evaporation. The exhibited rectification ratio higher than 106 at ±3 V, showed deep-ultraviolet-light detection reverse bias. spectral response solar-blind sensitivity high photoresponsivities 2.6–8.7 A/W wavelengths 200–260 nm. These values were 35–150 times those derived assuming the internal quantum efficiency to be unity. This fact...
Wide-bandgap semiconductors are expected to be applied solid-state lighting and power devices, supporting a future energy-saving society. While GaN-based white LEDs have rapidly become widespread in the industry, SiC- devices not yet achieved their popular use, like for lighting, despite having reached practical phase. What issues addressed such devices? In addition, other wide-bandgap as diamond oxides attracting focusing interest due promising functions especially power-device...
Giant photovoltaic effect due to bulk observed in multiferroic BiFeO3 thin films has triggered a renewed interest on photoferroelectric materials for applications. Tremendous advance been done improve power conversion efficiency (up up 8.1%) photoferroelectrics via absorption increase using narrow bandgap ferroelectrics. Other strategies, as it is the more efficient use of ferroelectric internal electric field, are ongoing. Moreover, by-product, several progress have also achieved...
Two types of nitrogen plasma sources, an electron cyclotron resonance (ECR) source and a radio frequency (rf) source, were used for the growth GaN by molecular beam epitaxy (MBE). film quality was correlated with optical emission characteristics each type employed. The best films those grown using rf source. This found to emit much larger fraction atomic 1st-positive series excited in contrast ECR which mainly produced 2nd-positive ions when operated under same conditions. benefit...
An oxide semiconductor of β-Ga2O3 has a natural solar-blind sensitivity due to its large bandgap 4.8 eV. To evaluate potential, flame detector was fabricated using conductive single crystal substrate applying simple method without epitaxy and vacuum processes. The structure is poly(3,4-ethylene dioxythiophene) complex with polystyrene sulfonic acid (PEDOT–PSS) Schottky contact/a semi-insulating layer β-Ga2O3/n-type region β-Ga2O3/an In ohmic contact. spectral response the exhibited...
Abstract The recent progress and development of corundum-structured III-oxide semiconductors are reviewed. They allow bandgap engineering from 3.7 to ∼9 eV function engineering, leading highly durable electronic devices deep ultraviolet optical as well multifunctional devices. Mist chemical vapor deposition can be a simple safe growth technology is advantageous for reducing energy cost the growth. This favorable wide commercial use at low cost. promising candidates new contributing...
Following the previous achievement of highly crystalline α-Ga 2 O 3 thin films on c -plane sapphire, growth corundum-structured α-(Al x Ga 1- ) was examined aiming at future application /Ga heterostructures to power devices and other functional devices. The results show control band gap up 0.81 7.8 eV, respectively, maintaining dominant corundum structure. transmission electron microscope observation suggested formation crystallographically good interface without severe generation threading...
Corundum-structured α-Ga 2 O 3 epitaxial thin films were grown on c -plane α-Al (sapphire) substrates by a mist chemical vapor deposition method. To reveal the defect structures, film was observed high-resolution transmission electron microscopy (TEM). We found that in-plane compressive stressed from substrate. Although misfit dislocations periodically generated at /α-Al interface owing to large lattice mismatches between and , 3.54% ( -axis) 4.81% -axis), most of did not thread through...
We report the fabrication of electrical conductive tin-doped α-Ga 2 O 3 thin films on c -plane sapphire substrates. The mist chemical vapor deposition method brought with high crystallinity without noticeable other phases, as highlighted by full-width X-ray diffraction ω-scan rocking curves small 40 arcsec, for tin atomic density in film upto ∼10 20 cm -3 . resistivity decreased more doping tin, and minimum exhibited n-type conductivity Hall mobility 2.8 V -1 s carrier 2.7 ×10 19
Abstract We achieved the successful fabrication of Sn-doped α-Ga 2 O 3 thin films with higher electron mobility and wider conductivity controls by improving crystal quality. showed n-type a maximum 24 cm V −1 s . The carrier concentration was successfully controlled in range 10 17 –10 19 −3 Crystal defects such as dislocations severely compensate free carriers restrict at low concentrations. Therefore, to achieve further control mobility, crystallinity is necessary.
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 Homoepitaxial single-crystal beta gallium oxide (β-Ga 2 O 3 ) films were fabricated by the mist chemical vapor deposition method. The crystallinity of grown markedly depended on growth temperature, and optimum temperatures found to be 700–800 °C. Using unintentionally doped β-Ga Sn-doped (010) substrates, fabrication Schottky barrier diodes was demonstrated. Furthermore, we electrically conductive semi-insulating Fe-doped substrates. carrier concentrations between 1 × 10 18 5 20 cm...
We demonstrate the epitaxial lateral overgrowth of α-Ga2O3 by halide vapor phase epitaxy. prepared patterned SiO2 masks on a (0001) α-Ga2O3/sapphire template, and then islands were regrown selectively mask windows. The grew vertically laterally to coalesce with each other. Facet control was achieved controlling growth temperature, inclined facets developed decreasing temperature. Transmission electron microscopy revealed that crystal quality improved owing both blocking dislocations...
Corundum-structured oxides have been attracting much attention as next-generation power device materials. A corundum-structured α-Ga2O3 successfully demonstrated operations of Schottky barrier diodes (SBDs) with the lowest on-resistance 0.1 mΩ cm2. The SBDs a mounting TO220 also showed low switching-loss properties capacitance 130 pF. Moreover, thermal resistance was 13.9 °C/W, which is comparable to that SiC (12.5 °C/W). On other hand, α-(Rh,Ga)2O3 p-type conductivity, confirmed by Hall...
Corundum-structured iridium oxide (α-Ir2O3), showing p-type conductivity, is a strong candidate to form high-quality pn heterojunctions with α-Ga2O3. We fabricated α-Ir2O3/α-Ga2O3 heterojunction diodes and they showed well-defined rectifying current-voltage (I-V) characteristics the turn-on voltage of about 2.0 V. The band alignment at interface was investigated by X-ray photoemission spectroscopy, revealing staggered-gap (type-II) valence- conduction-band offsets 3.34 eV 1.04 eV,...
Abstract Efforts have been made to reduce the density of defects in corundum-structured α-Ga 2 O 3 thin films on sapphire substrates by applying quasi-graded α-(Al x Ga 1− ) buffer layers. Transmission electron microscopy images revealed that most strains were located layers, and total dislocations was successfully decreased more than one order magnitude compared with without is, screw edge dislocation densities about × 10 8 6 cm −2 , respectively.
Ultra-wide bandgap p-type α-(Ir,Ga)2O3 films with bandgaps of up to 4.3 eV have been obtained by unintentional doping or Mg doping. For Mg-doped films, Hall-effect measurements revealed a hole concentration 9.9 × 1018 8.1 1019 cm−3 and mobility 0.13 − 0.92 cm2/V s, respectively. A preliminary test pn junction diode composed n-type α-Ga2O3 did not show catastrophic breakdown in the reverse direction until 100 V current on/off ratio at +3 V/−3V was 5 105. Since take same crystal structure are...
Routes to semi-stable phases of Ga2O3 are the subject extended discussions based on review growth methods, conditions, and precursors in works that report other than thermally stable β phase. The focus here is mist chemical vapor deposition because it has produced single-phase α, γ, ε (or κ) terms substrate materials, features this method for phase control emphasized. Recent reports by technology give a deeper understanding how determine phases, increasing opportunities fully utilize novel...