| 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. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
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| 8. |
- Mock, Alyssa, et al.
(författare)
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Band-to-band transitions, selection rules, effective mass, and excitonic contributions in monoclinic beta-Ga2O3
- 2017
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 96:24
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Tidskriftsartikel (refereegranskat)abstract
- We employ an eigenpolarization model including the description of direction dependent excitonic effects for rendering critical point structures within the dielectric function tensor of monoclinic beta-Ga2O3 yielding a comprehensive analysis of generalized ellipsometry data obtained from 0.75-9 eV. The eigenpolarization model permits complete description of the dielectric response. We obtain, for single-electron and excitonic band-to-band transitions, anisotropic critical point model parameters including their polarization vectors within the monoclinic lattice. We compare our experimental analysis with results from density functional theory calculations performed using the Gaussian-attenuation-Perdew-Burke-Ernzerhof hybrid density functional. We present and discuss the order of the fundamental direct band-to-band transitions and their polarization selection rules, the electron and hole effective mass parameters for the three lowest band-to-band transitions, and their excitonic contributions. We find that the effective masses for holes are highly anisotropic and correlate with the selection rules for the fundamental band-to-band transitions. The observed transitions are polarized close to the direction of the lowest hole effective mass for the valence band participating in the transition.
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| 9. |
- 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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| 10. |
- Schubert, Mathias, et al.
(författare)
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Phonon properties: Phonon and free charge carrier properties in monoclinic-symmetry ß-Ga2O3
- 2020
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Ingår i: Gallium Oxide. - Cham : Springer. - 9783030371524 - 9783030371555 - 9783030371531 ; , s. 501-534
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We present and discuss the complete set of infrared-active phonon modes in monoclinic-symmetry crystal modification gallium oxide (gallia, ββ-Ga2O3). The phonon mode set is obtained from a comprehensive analysis of generalized spectroscopic ellipsometry data in the farinfrared and infrared spectral regions investigating various n-type electrically conductive single crystal samples with different free electron volume density parameters cut under different orientations. The analysis of the ellipsometry data is performed using an eigendielectric displacement vector summation (EDVS) approach. In this approach, the effect of the free charge carriers onto the lattice modes of intrinsic ββ-Ga2O3 are removed by calculation. Density functional theory calculations are performed in the general gradient approximation and all phonon modes at the Brillouin-center and their displacement direction dependencies are obtained. Transverse and longitudinal optical phonon mode parameters polarized within the monoclinic plane as well as perpendicular to the monoclinic plane agree excellently between experiment and theory. We also present and discuss the directional limiting frequency parameters within the monoclinic plane, the shape and anisotropy of the reststrahlen band, and the order of the phonon modes in semiconductors with polar phonon modes and monoclinic crystal structure. We further present and discuss the effect of coupling of longitudinal optical phonons with free charge carriers, leading to longitudinal-phonon-plasmon coupled modes. We reveal that the coupled modes, which affect electric and thermal transport, change amplitude, frequency, and direction within the monoclinic plane as a function of free electron concentration. Finally, we show optical Hall effect measurements, and provide experimentally determined effective electron mass parameters in ββ-Ga2O3 for moderately-doped n-type samples.
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