| 1. |
- Goto, Ken, et al.
(författare)
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Halide vapor phase epitaxy of Si doped beta-Ga2O3 and its electrical properties
- 2018
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Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 666, s. 182-184
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Tidskriftsartikel (refereegranskat)abstract
- Silicon doped homoepitaxial films were grown on beta-gallium oxide (001) substrates by halide vapor phase epitaxy using gallium monochloride, oxygen and silicon tetrachloride gases as precursors. It was confirmed that the n-type carrier density at room temperature was almost equal to the doped silicon concentration, which was controlled in the range of 10(15) to 10(18) cm(-3). In the doped film with the carrier density of 1x10(16) cm(-3), the activation energy and the mobility at room temperature were 45.6 meV and 145 cm(2)/V.s, respectively. The carrier scattering mechanism in the low carrier density film was dominated by optical phonon scattering with the phonon energy of 33 meV. These results suggest that the doped homoepitaxial film grown by halide vapor phase epitaxy is a high quality film with good crystallinity comparable to bulk crystals.
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| 2. |
- Goto, Ken, et al.
(författare)
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Study of Dislocations in Homoepitaxially and Heteroepitaxially Grown AlN Layers
- 2020
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Ingår i: Physica Status Solidi (a) applications and materials science. - : WILEY-V C H VERLAG GMBH. - 1862-6300 .- 1862-6319. ; 217:24
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Tidskriftsartikel (refereegranskat)abstract
- Dislocation densities in AlN layers grown on c-plane sapphire and physical vapor transport-grown AlN (PVT-AlN) (0001) substrates, by metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE), respectively, are evaluated from the density of etch pits formed in sodium hydroxide (NaOH)/potassium hydroxide (KOH) eutectic heated to 450 degrees C. In the heteroepitaxial layers grown by MOVPE on the sapphire substrates, etch pits with different sizes are formed. Cross-sectional transmission electron microscopy (TEM) observations reveal that the large, medium, and small pits, with densities of 1.4 x 10(6), 2.6 x 10(7), and 6.9 x 10(9) cm(-2), respectively, correspond to screw, mixed, and edge dislocations, respectively. In contrast, in the homoepitaxial layers grown by HVPE on the PVT-AlN substrates, only one kind of etch pit with uniform size corresponding to the edge dislocations is formed with a density of 10(3)-10(4) cm(-2). Cross-sectional TEM observation confirms that the edge dislocations in the homoepitaxial layer propagate from the substrate through the interface, which indicates that the dislocation density does not increase during homoepitaxial growth by HVPE. The HVPE-AlN homoepitaxial layers grown on the PVT-AlN substrates are found to have very low dislocation density.
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| 3. |
- 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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| 4. |
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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- Knight, Sean, et al.
(författare)
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Electron effective mass in Sn-doped monoclinic single crystal beta-gallium oxide determined by mid-infrared optical Hall effect
- 2018
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 112:1
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Tidskriftsartikel (refereegranskat)abstract
- The isotropic average conduction band minimum electron effective mass in Sn-doped monoclinic single crystal beta-Ga2O3 is experimentally determined by the mid-infrared optical Hall effect to be (0.2846 +/- 0.013)m(0) combining investigations on (010) and ((2) over bar 01) surface cuts. This result falls within the broad range of values predicted by theoretical calculations for undoped beta-Ga2O3. The result is also comparable to recent density functional calculations using the Gaussian-attenuation-Perdew-Burke-Ernzerhof hybrid density functional, which predict an average effective mass of 0.267m(0). Within our uncertainty limits, we detect no anisotropy for the electron effective mass, which is consistent with most previous theoretical calculations. We discuss upper limits for possible anisotropy of the electron effective mass parameter from our experimental uncertainty limits, and we compare our findings with recent theoretical results. Published by AIP Publishing.
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| 9. |
- Konishi, Keita, et al.
(författare)
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Comparison of O-2 and H2O as oxygen source for homoepitaxial growth of beta-Ga2O3 layers by halide vapor phase epitaxy
- 2018
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Ingår i: Journal of Crystal Growth. - : ELSEVIER SCIENCE BV. - 0022-0248 .- 1873-5002. ; 492, s. 39-44
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Tidskriftsartikel (refereegranskat)abstract
- Homoepitaxial growth of p-Ga2O3 layers by halide vapor phase epitaxy (HVPE) using O-2 or H2O as an oxygen source was investigated by thermodynamic analysis, and compared with measured properties after growth. The thermodynamic analysis revealed that Ga2O3 growth is expected even at 1000 C-degrees using both oxygen sources due to positive driving forces for Ga2O3 deposition. The experimental results for homoepitaxial growth on (0 0 1) beta-Ga2O3 substrates showed that the surfaces of the layers grown with H2O were smoother than those grown with O-2, although the growth rate with H2O was approximately half that with O-2. However, in the homoepitaxial layer grown using H2O, incorporation of Si impurities with a concentration almost equal to the effective donor concentration (2 x 10(16)cm (3)) was confirmed, which was caused by decomposition of the quartz glass reactor due to the presence of hydrogen in the system. (C) 2018 Elsevier B.V. All rights reserved.
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| 10. |
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