| 1. |
- Higashiwaki, Masataka, et al.
(författare)
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Current Status of Gallium Oxide-Based Power Device Technology
- 2015
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Ingår i: 2015 IEEE COMPOUND SEMICONDUCTOR INTEGRATED CIRCUIT SYMPOSIUM (CSICS). - : IEEE. - 9781479984947
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Konferensbidrag (refereegranskat)abstract
- Gallium oxide (Ga2O3) possesses excellent material properties especially for power device applications. It is also attractive from an industrial viewpoint since large -size, high quality wafers can be manufactured by using simple methods. These two features have drawn much attention to Ga2O3 as a new wide bandgap semiconductor following SiC and GaN. In this report, we describe the recent progress in development on fundamental technologies for Ga2O3 devices, covering wafer production from melt -grown bulk single crystals, homoepitaxial thin-film growth by halide vapor phase epitaxy, as well as device processing and characterization of metal -oxide -semiconductor field-effect transistors and Schottky barrier diodes.
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| 2. |
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| 3. |
- Higashiwaki, Masataka, et al.
(författare)
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Temperature-dependent capacitance-voltage and current-voltage characteristics of Pt/Ga2O3 (001) Schottky barrier diodes fabricated on n(-)-Ga2O3 drift layers grown by halide vapor phase epitaxy
- 2016
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 108:13, s. 133503-
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the temperature-dependent electrical properties of Pt/Ga2O3 Schottky barrier diodes (SBDs) fabricated on n(-)-Ga2O3 drift layers grown on single-crystal n(+)-Ga2O3 (001) substrates by halide vapor phase epitaxy. In an operating temperature range from 21 degrees C to 200 degrees C, the Pt/Ga2O3 (001) Schottky contact exhibited a zero-bias barrier height of 1.09-1.15 eV with a constant near-unity ideality factor. The current-voltage characteristics of the SBDs were well-modeled by thermionic emission in the forward regime and thermionic field emission in the reverse regime over the entire temperature range. (C) 2016 AIP Publishing LLC.
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| 4. |
- Hirasaki, Takahide, et al.
(författare)
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Growth of thick and high crystalline quality InGaN layers on GaN (000(1)over-bar) substrate using tri-halide vapor phase epitaxy
- 2016
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Ingår i: Journal of Crystal Growth. - : ELSEVIER SCIENCE BV. - 0022-0248 .- 1873-5002. ; 456, s. 145-150
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Tidskriftsartikel (refereegranskat)abstract
- The growth of thick InGaN layers on free-standing GaN (000 (1) over bar substrates was studied using tri-halide vapor phase epitaxy. It was found that high-indium-content InGaN can be grown under higher InCl3 input partial pressure at higher growth temperature, which allows the fabrication of a high crystalline quality InGaN layer with a smooth surface morphology. Using the growth conditions of high InCl3 input partial pressure and high growth temperature, crack- and droplet-free InGaN layers with a thickness of over 10 mu m and with an indium fraction of 0.05 were successfully grown. Although the surface showed many hillocks, the number of hillocks was reduced upon growth of thicker InGaN layers. Photoluminescence measurements confirm that thick InGaN layers could be successfully grown without degradation of the crystalline quality. (C) 2016 Elsevier B.V. All rights reserved.
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| 5. |
- Hirasaki, Takahide, et al.
(författare)
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Investigation of NH3 input partial pressure for N-polarity InGaN growth on GaN substrates by tri-halide vapor phase epitaxy
- 2016
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Ingår i: Japanese Journal of Applied Physics. - : IOP PUBLISHING LTD. - 0021-4922 .- 1347-4065. ; 55:5, s. 05FA01-
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Tidskriftsartikel (refereegranskat)abstract
- The influence of NH3 input partial pressure on N-polarity InGaN grown by tri-halide vapor phase epitaxy was investigated. It was found that surface morphology, solid composition and optical properties were affected by NH3 input partial pressure. As shown in thermodynamic analyses, the indium content increased due to an increase in the driving force for InN deposition caused by increased NH3 input partial pressure. In addition, the deep level emission around 2.1 eV in photoluminescence measurements drastically decreased at higher NH3 input partial pressures. Ab initio calculations and subsequent secondary ion mass spectrometry measurements suggested the reduction of metal-vacancies and/or carbon impurity incorporation in the InGaN layers. (C) 2016 The Japan Society of Applied Physics
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| 6. |
- Masuda, Rui, et al.
(författare)
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Improvements in Optical Properties of (0001) ZnO Layers Grown on (0001) Sapphire Substrates by Halide Vapor Phase Epitaxy Using Thick Buffer Layers
- 2012
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Ingår i: Japanese Journal of Applied Physics. - : Japan Society of Applied Physics. - 0021-4922 .- 1347-4065. ; 51:3, s. 031103-
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of (0001) ZnO layers grown at 1000 degrees C on (0001) sapphire substrates by halide vapor phase epitaxy (HVPE) were investigated by various photoluminescence (PL) measurements. A layer grown with a H2O/ZnCl2 (VI/II) ratio of 20 on a 0.4-mu m-thick buffer layer exhibited a significant near-band-edge (NBE) peak blueshift and degraded internal quantum efficiency (eta(int)) due to residual compressive stress. Growth with a VI/II ratio of 600 diminished the NBE peak blueshift; however, deep level emission and a reduction of PL decay time (tau(PL)) were caused by point defects generated by excess O source supply. A layer without the NBE peak blueshift and deep level emission was realized by growth with a VI/II ratio of 20 and a buffer layer of 0.8 mu m. The eta(int) and tau(PL) for HVPE-grown layers could be improved to 4.1% and 122.8 ps by using the thick buffer layer and appropriate VI/II ratio.
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| 7. |
- Murakami, Hisashi, et al.
(författare)
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Homoepitaxial growth of beta-Ga2O3 layers by halide vapor phase epitaxy
- 2015
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Ingår i: Applied Physics Express. - : Japan Society of Applied Physics. - 1882-0778. ; 8:1, s. 015503-
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Tidskriftsartikel (refereegranskat)abstract
- Thick high-purity beta-Ga2O3 layers of high crystalline quality were grown homoepitaxially by halide vapor phase epitaxy (HVPE) using gaseous GaCl and O-2 on (001) beta-Ga2O3 substrates prepared by edge-defined film-fed growth. The surface morphology and structural quality of the grown layer improved with increasing growth temperature. X-ray diffraction omega-rocking curves for the (002) and (400) reflections for the layer grown at 1000 degrees C had small full widths at half maximum. Secondary ion mass spectrometry and electrical characteristics revealed that the growth of high-purity beta-Ga2O3 layers with low effective donor concentration (N-d - N-a less than 10(13) cm(-3)) is possible by HVPE. (C) 2015 The Japan Society of Applied Physics
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| 8. |
- Togashi, Rie, et al.
(författare)
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Effect of High NH3 Input Partial Pressure on Hydride Vapor Phase Epitaxy of InN Using Nitrided (0001) Sapphire Substrates
- 2013
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Ingår i: Japanese Journal of Applied Physics. - : Japan Society of Applied Physics. - 0021-4922 .- 1347-4065. ; 52:8
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the source gas supply sequence prior to growth and the NH3 input partial pressure (PoNH3) on the nucleation of InN islands during the initial stages of hydride vapor phase epitaxy on a nitrided (0001) sapphire substrate was investigated. The crystalline quality of the InN layer after subsequent lateral growth was also examined. When NH3 was flowed prior to growth, single-crystal hexagonal InN islands formed. When InN was grown with a higher PoNH3, the number of InN islands decreased remarkably while their diameter increased. The crystalline quality of InN grown on the hexagonal islands with a high PoNH3 significantly improved with increasing growth time. A strong PL spectrum was observed only from InN layers grown with a high PoNH3. It was thus revealed that an NH3 preflow and a high PoNH3 are effective for producing InN with high crystalline quality and good optical and electrical properties.
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| 9. |
- Togashi, Rie, et al.
(författare)
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High rate InN growth by two-step precursor generation hydride vapor phase epitaxy
- 2015
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 422, s. 15-19
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Tidskriftsartikel (refereegranskat)abstract
- The increase of InN growth rate by a newly developed two-step precursor generation hydride vapor phase epitaxy (HVPE) was investigated for the preparation of freestanding InN and InGaN substrates. An elevated growth rate was achieved by the complete conversion of InCl generated in the first source zone to InCl3 in the second source zone, by the supply of additional Cl2. The growth rate reached 12.4 μm/h at a growth temperature of 600 °C, and the rate was observed to decrease above this temperature. Specular InN layers grown at 650 °C exhibited a sharp room temperature photoluminescence peak at 0.73 eV with a bulk electron concentration of 1.2×1018 cm−3.
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| 10. |
- Togashi, Rie, et al.
(författare)
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Thermal and chemical stabilities of group-III sesquioxides in a flow of either N-2 or H-2
- 2016
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Ingår i: Japanese Journal of Applied Physics. - : IOP PUBLISHING LTD. - 0021-4922 .- 1347-4065. ; 55:12
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Tidskriftsartikel (refereegranskat)abstract
- The thermal and chemical stabilities of group-III sesquioxides (Al2O3, Ga2O3, and In2O3) were comparatively investigated at an atmospheric pressure at heat treatment temperatures ranging from 250 to 1450 degrees C in a flow of either N-2 or H-2. In a flow of N-2, the thermal decomposition of alpha-Al2O3 was not observed at the temperatures investigated, while the decompositions of beta-Ga2O3 and c-In2O3 occurred above 1150 and 1000 degrees C, respectively, with no generation of group-III metal droplets on the surfaces. In contrast, the chemical reactions of alpha-Al2O3, beta-Ga2O3, and c-In2O3 began at low temperatures of 1150, 550, and 300 degrees C in a flow of H-2. Thus, the presence of H-2 in the gas flow significantly promotes the decomposition of group-III sesquioxides. The order of thermal and chemical stabilities (alpha-Al2O3 amp;gt;amp;gt; beta-Ga2O3 amp;gt; c-In2O3) obtained experimentally was verified by thermodynamic analysis, which also clarified dominant decomposition reactions of group-III sesquioxides. (C) 2016 The Japan Society of Applied Physics
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| 11. |
- Togashi, Rie, et al.
(författare)
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Thermal stability of beta-Ga2O3 in mixed flows of H-2 and N-2
- 2015
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Ingår i: Japanese Journal of Applied Physics. - : Japan Society of Applied Physics. - 0021-4922 .- 1347-4065. ; 54:4, s. 041102-
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Tidskriftsartikel (refereegranskat)abstract
- The thermal stability of beta-Ga2O3(010) substrates was investigated at atmospheric pressure between 250 and 1450 degrees C in a flow of either N-2 or a mixture of H-2 and N-2 using a radio-frequency induction furnace. The beta-Ga2O3 surface was found to decompose at and above 1150 degrees C in N-2, while the decomposition of beta-Ga2O3 began at only 350 degrees C in the presence of H-2. Heating beta-Ga2O3 substrates in gas flows containing different molar fractions of H-2 demonstrated that the decomposition was promoted by increasing the H-2 molar fractions. Thermodynamic analysis showed that the dominant reactions are Ga2O3(s) = Ga2O(g) + O-2(g) in N-2 and Ga2O3(s) + 2H(2)(g) = Ga2O(g) = 2H(2)O(g) in a mixed flow of H-2 and N-2. The second-order reaction with respect to H-2 determined for the mixed flows agrees with the experimental results for the dependence of the beta-Ga2O3 decomposition rates on the H-2 molar fraction.
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| 12. |
- Tojo, Shunsuke, et al.
(författare)
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Influence of high-temperature processing on the surface properties of bulk AlN substrates
- 2016
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Ingår i: Journal of Crystal Growth. - : ELSEVIER SCIENCE BV. - 0022-0248 .- 1873-5002. ; 446, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- Deep-level luminescence at 3.3 eV related to the presence of Al vacancies (V-Al) was observed in room temperature photoluminescence (RT-PL) spectra of homoepitaxial AlN layers grown at 1450 degrees C by hydride vapor-phase epitaxy (HVPE) and cooled to RT in a mixture of H-2 and N-2 with added NH3. However, this luminescence disappeared after removing the near surface layer of AlN by polishing. In addition, the deep-level luminescence was not observed when the post-growth cooling of AlN was conducted without NH3. Secondary ion mass spectrometry (SIMS) studies revealed that although the point defect density of the interior of the AlN layers remained low, the near surface layer cooled in the presence of NH3 was contaminated by Si impurities due to both suppression of the surface decomposition by the added NH3 and volatilization of Si by decomposition of the quartz reactor walls at high temperatures. The deep-level luminescence reappeared after the polished AlN wafers were heated in presence of NH3 at temperatures above 1400 degrees C. The surface contamination by Si is thought to generate V-Al near the surface by lowering their formation energy due to the Fermi level effect, resulting in deep-level luminescence at 3.3 eV caused by the shallow donor (Si) to V-Al transition. (C) 2016 Elsevier B.V. All rights reserved.
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