Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-11-30T07:38:39.178Z Has data issue: false hasContentIssue false
  • English
  • Français

Device processing and junction formation needs for ultra-high power Ga2O3 electronics

Published online by Cambridge University Press:  29 January 2019

Fan Ren ,
J.C. Yang ,
Chaker Fares  and
S.J. Pearton
Fan Ren
Affiliation:
Department of Chemical Engineering, University of Florida, Gainesville FL 32611, USA
J.C. Yang
Affiliation:
Department of Chemical Engineering, University of Florida, Gainesville FL 32611, USA
Chaker Fares
Affiliation:
Department of Chemical Engineering, University of Florida, Gainesville FL 32611, USA
S.J. Pearton*
Affiliation:
Department of Materials Science and Engineering, University of Florida, Gainesville FL 32611, USA
*
Address all correspondence to S.J. Pearton at [email protected]
Get access

Abstract

A review is given of the future device processing needs for Ga2O3 power electronics. The two main devices employed in power converters and wireless charging systems will be vertical rectifiers and metal oxide semiconductor field effect transistors (MOSFETs). The rectifiers involve thick epitaxial layers on conducting substrates and require stable Schottky contacts, edge termination methods to reduce electric field crowding, dry etch patterning in the case of trench structures, and low resistance Ohmic contacts in which ion implantation or low bandgap interfacial oxides are used to minimize the specific contact resistance. The MOSFETs also require spatially localized doping enhancement for low source/drain contact resistance, stable gate insulators with acceptable band offsets relative to the Ga2O3 to ensure adequate carrier confinement, and enhancement mode capability. Attempts are being made to mitigate the absence of p-type doping capability for Ga2O3 by developing p-type oxide heterojunctions with n-type Ga2O3. Success in this area would lead to minority carrier devices with better on-state performance and a much-improved range of functionality, such as p-i-n diodes, Insulated Gate Bipolar Transistors, and thyristors.

Type
Prospective Articles
Information
MRS Communications , Volume 9 , Issue 1 , March 2019 , pp. 77 - 87
Copyright
Copyright © Materials Research Society 2019 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1.Galazka, Z.: β-Ga2O3 for wide-bandgap electronics and optoelectronics. Semicond. Sci. Technol. 33, 113001 (2018). https://doi.org/10.1088/1361-6641/aadf78.Google Scholar
2.Bayraktaroglu, B.: Assesment of Gallium Oxide Technology, Air Force Research Lab, Devices for Sensing Branch, Aerospace Components and Subsystems Division, Report AFRL-RY-WP-TR-2017-0167 (2017).Google Scholar
3.Higashiwaki, M. and Jessen, G.H.: Guest editorial: the dawn of gallium oxide microelectronics. Appl. Phys. Lett. 112, 060401 (2018).Google Scholar
4.Tadjer, M.J., Mahadik, N.A., Wheeler, V., Glaser, E.R., Ruppalt, L., and Koehler, A.D.: Editors’ choice communication-A (001) β-Ga2O3 MOSFET with +2.9 V threshold voltage and HfO2 gate dielectric. ECS J. Solid State Sci. Technol. 5, P468–P470 (2016).Google Scholar
5.Wong, M.H., Sasaki, K., Kuramata, A., Yamakoshi, S., and Higashiwaki, M.: Field-plated Ga2O3 MOSFETs with a breakdown voltage of over 750 V. IEEE Electron Device Lett. 37, 212–215 (2016).Google Scholar
6.Pearton, S.J., Yang, J.C., Carey, P.H., Ren, F, Kim, J., Tadjer, M.J., and Mastro, M.A.: A review of Ga2O3 materials, processing, and devices. Appl. Phys. Rev. 5, 011301 (2018).Google Scholar
7.Cheng, X.: Overview of recent progress of semiconductor power devices based on wide bandgap materials. IOP Conf. Ser.: Mater. Sci. Eng. 439, 022033 (2018). https://doi.org/10.1088/1757-899X/439/2/022033.Google Scholar
8.Singh, R. and Sundaresan, S.: 1200 V SiC Schottky rectifiers optimized for ≥250 °C operation with low junction capacitance Applied Power Electronics Conference and Exposition, pp. 226–228 (2013).Google Scholar
9.Eum, Y., Oyama, K., and Otake, N.: Highly reliable GaN MOS-HFET with high short-circuit capability International Symposium on Power Semiconductor Devices and Ic's, pp. 195–198 (2017).Google Scholar
10.Varley, J.B., Janotti, A., Franchini, C., and Van de Walle, C.G.: Role of self-trapping in luminescence and p-type conductivity of wide-band-gap oxides. Phys. Rev. B 85, 081109(R) (2012).Google Scholar
11.Neal, A.T., Mou, S., Rafique, S., Zhao, H., Ahmadi, E., Speck, J.S., Stevens, K.T., Blevins, J.D., Thomson, D.B., Moser, N., Chabak, K.D., and Jessen, G.H.: Donors and deep acceptors in β-Ga2O3. Appl. Phys. Lett. 113, 062101 (2018); https://doi.org/10.1063/1.5034474.Google Scholar
12.Sasaki, K., Higashiwaki, M., Kuramata, A., Masui, T., and Yamakoshi, S.: Si-ion implantation doping in beta-Ga2O3 and its application to fabrication of low-resistance ohmic contacts. Appl. Phys. Express 6, 086502 (2013).Google Scholar
13.Higashiwaki, M., Sasaki, K., Kuramata, A., Masui, T., and Yamakoshi, S.: Gallium oxide (Ga2O3) metal-semiconductor field-effect transistors on single-crystal β-Ga2O3 (010) substrates. Appl. Phys. Lett. 100, 013504 (2012).Google Scholar
14.Watahiki, T., Yuda, Y., Furukawa, A., Yamamuka, M., Takiguchi, Y., and Miyajima, S.: Heterojunction p-Cu2O/n-Ga2O3 diode with high breakdown voltage. Appl. Phys. Lett. 111, 222104 (2017).Google Scholar
15.Tadjer, M.A., Mahadik, N.A., Freitas, J.A., Glaser, E.A., Koehler, A.D., Luna, L.E., Feigelson, B.N., Hobart, K.D., Kub, F.J., and Kuramata, A.: Ga2O3 Schottky barrier and heterojunction diodes for power electronics applications, Proc. SPIE 10532,Gallium Nitride Materials and Devices XIII, 1053212 (23 February 2018); doi: 10.1117/12.2292211.Google Scholar
16.Kokubun, Y., Kubo, S., and Nakagomi, S.: All-oxide p–n heterojunction diodes comprising p-type NiO and n-type β- Ga2O3. Appl. Phys. Expr. 9, 091101 (2016).Google Scholar
17.Nakagomi, S., Hiratsuka, K., Kakuda, Y., and Kokubun, Y.: Beta-gallium oxide/SiC heterojunction diodes with high rectification ratios. ECS J. Solid State Sci. Technol. 6, Q3030–Q3034 (2017).Google Scholar
18.Lee, J., Flitsiyan, E., Chernyak, L., Yang, J., Ren, F., Pearton, S.J., Meyler, B., and Salzman, Y.J.: Effect of 1.5 MeV electron irradiation on β-Ga2O3 carrier lifetime and diffusion length. Appl. Phys. Lett. 112, 082104 (2018); https://doi.org/10.1063/1.5011971.Google Scholar
19.Higashiwaki, M., Sasaki, K., Wong, M.H., Kamimura, T., Krishnamurthy, D., Kuramata, A., Masui, T., and Yamakoshi, S.: Depletion-mode Ga2O3 MOSFETs on β-Ga2O3 (010) substrates with Si-ion-implanted channel and contacts, Electron Devices Meeting (IEDM), 2013 IEEE International, pages 28–32. IEEE, 2013.Google Scholar
20.Chikoidze, E., Fellous, A., Perez-Tomas, A., Sauthier, G., Tchelidze, T., Ton-That, C., Huynh, T., Phillips, M., Russell, S., Jennings, M., Berini, B., Jomard, F., and Dumont, Y.: P-type β-gallium oxide: a new perspective for power and optoelectronic devices. Mater. Today Physics 3, 118–126 (2017). https://doi.org/10.1016/j.mtphys.2017.10.002.Google Scholar
21.Kyrtsos, A., Matsubara, M., and Bellotti, E.: On the feasibility of p-type Ga2O3. Appl. Phys. Lett. 112, 032108 (2018); https://doi.org/10.1063/1.5009423.Google Scholar
22.Tadjer, M.A., Anderson, T., Hobart, K.D., Feygelson, T.I., Caldwell, J.D., Eddy, C.R., Kub, F.J., Butler, J.E., Pate, B., and Melngailis, J.: Reduced self-heating in AlGaN/GaN HEMTs using nanocrystalline diamond heat-spreading films. IEEE Electron Dev. Lett. 33, 23–25 (2012).Google Scholar
23.Anderson, T.J., Koehler, A.D., Hobart, K.D., Tadjer, M.J., Feygelson, T.I., Hite, J.K., Pate, B., Kub, F.J., and Eddy, C.R.: Nanocrystalline diamond-gated AlGaN/GaN HEMT. IEEE Electron Dev. Lett. 34, 1382–1384 (2013).Google Scholar
24.Meyer, D., Feygelson, T., Anderson, T., Roussos, J., Tadjer, M., Downey, B., Katzer, D., Pate, B., Ancona, M., Koehler, A., Hobart, K.D., and Eddy, C.: Large-signal RF performance of nanocrystalline diamond coated AlGaN/GaN high electron mobility transistors. IEEE Electron Dev. Lett. 35, 1013–1015 (2014).Google Scholar
25.Chabak, K., Moser, N., Green, A.J., Walker, D.E., Tetlak, S.E., Heller, E., Crespo, A., Fitch, R., McCandless, J., Leedy, K., Baldini, M., Wagner, G., Galazka, Z., Li, X., and Jessen, G.: Enhancement-mode Ga2O3 wrap-gate fin field-effect transistors on native (100) β-Ga2O3 substrate with high breakdown voltage. Appl. Phys. Lett. 109, 213501 (2016). https://doi.org/10.1063/1.4967931.Google Scholar
26.Ahmadi, E., Koksaldi, O.S., Zheng, X., Mates, T., Oshima, Y., Mishra, U., and Speck, J.: Demonstration of β-(Alx Ga1−x)2O3/β-Ga2O3 modulation doped field-effect transistors with Ge as dopant grown via plasma-assisted molecular beam epitaxy. Appl. Phys. Expr. 10, 071101 (2017). https://doi.org/10.7567/APEX.10.071101.Google Scholar
27.Krishnamoorthy, S., Xia, Z., Joishi, C., Zhang, Y., McGlone, J., Johnson, J., Brenner, M., Arehart, A.R., Hwang, J., Lodha, S., and Rajan, S.: Modulation-doped β-(Al0.2Ga0.8)2O3/Ga2O3 field-effect transistor. Appl. Phys. Lett. 111, 023502 (2017).Google Scholar
28.Zhang, Y., Joishi, C., Xia, X., Brenner, M., Lodha, S., and Rajan, S.: Demonstration of β-(AlxGa1−x)2O3/Ga2O3 double heterostructure field effect transistors. Appl. Phys. Lett. 112, 233503 (2018). https://doi.org/10.1063/1.5037095.Google Scholar
29.Zhang, Y., Neal, A., Xia, S., Joishi, C., Johnson, J.M., Zheng, Y., Bajaj, S., Brenner, M., Dorsey, D., Chabak, K., Jessen, G., Hwang, J., Mou, S., Heremans, J.P., and Rajan, S: Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1−x)2O3/Ga2O3 heterostructures. Appl. Phys. Lett. 112, 173502 (2018).Google Scholar
30.Wakabayashi, R., Hattori, M., Yoshimatsu, K., Horiba, K., Kumigashira, H, and Ohtomo, A.: Band alignment at β-(AlxGa1-x)2O3/β-Ga2O3 (100) interface fabricated by pulsed-laser deposition. Appl. Phys. Lett. 112, 232103 (2018).Google Scholar
31.Takatsuka, A., Sasaki, K., Wakimoto, D., Thieu, Q., Koishikawa, R., Arima, J., Hirabayashi, J., Inokuchi, D., Fukumitsu, Y., Kuramata, A., and Yamakoshi, S.: Fast Recovery Performance of β-Ga2O3 Trench MOS Schottky Barrier Diodes, 76th Dev. Res. Conf. Proc., 2018. DOI: 10.1109/DRC.2018.8442267.Google Scholar
32.Yang, J.C., Ren, F., Chen, Y.T., Liao, Y.T., Chang, C.W., Lin, J., Tadjer, M., Pearton, S.J., and Kuramata, A.: Dynamic switching characteristics of 1 a forward current β-Ga2O3 rectifiers. IEEE J. Electron Devices Society (2019). DOI: 10.1109/JEDS.2018.2877495.Google Scholar
33.Zolper, J.C.: Ion implantation in group III-nitride semiconductors: a tool for doping and defect studies. J. Crystal Growth 178, 157–167 (1997). https://doi.org/10.1016/S0022-0248(97)00076-6.Google Scholar
34.Wong, M.H., Lin, C.H., Kuramata, A., Yamakoshi, S., Murakami, H., Masataka, Y., and Higashiwaki, M.: Acceptor doping of β-Ga2O3 by Mg and N ion implantations. Appl. Phys. Lett. 113, 102103 (2018). https://doi.org/10.1063/1.5050040.Google Scholar
35.Carey, P., Yang, J., Ren, F., Hays, D.C., Pearton, S.J., Jang, S., Kuramata, A., and Kravchenko, I.I.: Improvement of ohmic contacts on Ga2O3 through use of ITO-interlayers. J. Vac. Sci. Technol. B. 35, 061201 (2017).Google Scholar
36.Carey, P., Yang, J.C., Ren, F., Hays, D.C., Pearton, S.J., Jang, S., Kuramata, A., and Kravchenko, I.: Ohmic contacts on N-type Ga2O3 using AZO/Ti/Au. AIP. Adv. 7, 095313 (2017).Google Scholar
37.Hoshikawa, K., Ohba, E., Kobayashi, T., Yanagisawa, J., Miyagawa, C., and Nakamura, Y.: Growth of β-Ga2O3 single crystals using vertical Bridgman method in ambient air. J. Cryst. Growth 447, 36–41 (2016).Google Scholar
38.Togashi, R., Nomura, K., Eguchi, C., Fukizawa, T., Goto, K., Thieu, Q.T., Murakami, H., Kumagai, Y., Kuramata, A., and Yamakoshi, S.: Thermal stability of β-Ga2O3 in mixed flows of H2 and N2. Japan. J. Appl. Phys. 54, 041102 (2015). http://dx.doi.org/10.7567/JJAP.54.041102.Google Scholar
39.Mu, W., Jia, Z., Yin, Y., Hu, Q., Li, Y., Wu, B., Zhang, J., and Tao, X.: High quality crystal growth and anisotropic physical characterization of β-Ga2O3 single crystals grown by EFG method. J. Alloys Compounds 714, 453 (2017).Google Scholar
40.Nikolaev, V.I., Maslov, V., Stepanov, S., Pechnikov, A., Krymov, V., Nikitina, I., Guzilova, L., Bougrov, V., and Romanov, A.: Growth and characterization of β-Ga2O3 crystals. J. Cryst. Growth 457, 132–136 (2017).Google Scholar
41.Yao, Y., Davis, R.F., and Porter, L.M.: Investigation of different metals as ohmic contacts to β-Ga2O3: comparison and analysis of electrical behavior, morphology and other physical properties. J. Electron. Mater. 46, 2053 (2017).Google Scholar
42.Yao, Y., Gangireddy, R., Kim, J., Das, K.K., Davis, R.F., and Porter, L.M.: Electrical behavior of β-Ga2O3 Schottky diodes with different Schottky metals. J. Vacuum Sci. Technol. B 35, 03D113 (2017).Google Scholar
43.Tadjer, M.: Ohmic Contacts to Ga2O3. In Gallium Oxide Technology, Devices and Applications, edited by Pearton, S., Mastro, M. and Ren, F. (Elsevier, Oxford, 2018), pp. 413–434.Google Scholar
44.Oshima, T., Wakabayashi, R., Hattori, M., Hashiguchi, A., Kawano, N., Sasaki, K., Masui, T., Kuramata, A., Yamakoshi, S., and Yoshimatsu, K.: Formation of indium–tin oxide ohmic contacts for β-Ga2O3. Japan J. Appl. Phys. 55, 1202B7 (2016).Google Scholar
45.Splith, D., Müller, S., Schmidt, F., Von Wenckstern, H., van Rensburg, J.J., Meyer, W.E., and Grundmann, M.: Determination of the mean and the homogeneous barrier height of Cu Schottky contacts on heteroepitaxial β-Ga2O3 thin films grown by pulsed laser deposition. Physica status solidi (a), 211, 40–47 (2014).Google Scholar
46.Higashiwaki, M., Konishi, K., Sasaki, K., Goto, K., Nomura, K., Thieu, Q., Togashi, R., Murakami, H., Kumagai, Y., Monemar, B., Koukitu, A., Kuramata, A., and Yamakoshi, S.: 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. Appl. Phys. Lett., 108, 133503 (2016).Google Scholar
47.Ahn, S., Ren, F., Yuan, L., Pearton, S.J., and Kuramata, A.: Temperature-dependent characteristics of Ni/Au and Pt/Au Schottky diodes on β-Ga2O3. ECS J. Solid State Sci. Technol. 6, P68–P72 (2017).Google Scholar
48.Armstrong, A., Crawford, M.H., Jayawardena, A., Ahyi, A., and Dhar, S.: Role of self-trapped holes in the photoconductive gain of β-gallium oxide Schottky diodes. J. Appl. Phys., 119, 103102 (2016). https://doi.org/10.1063/1.4943261.Google Scholar
49.Oh, S., Yang, G., and Kim, J.: Electrical characteristics of vertical Ni/β-Ga2O3 Schottky barrier diodes at high temperatures. ECS J. Solid State Sci. Technol. 6, Q3022–Q3025 (2017).Google Scholar
50.Farzana, E., Zhang, Z., Paul, P., Arehart, A.R., and Ringel, S.A.: Influence of metal choice on (010) β-Ga2O3 Schottky barrier properties. Appl. Phys. Lett. 110, 202102 (2017). https://doi.org/10.1063/1.4983610.Google Scholar
51.Schottky, W.: Deviations from Ohm's law in semiconductors. Physik. Zeitschr 41, 570–573 (1940).Google Scholar
52.Mönch, W.: Valence-band offsets of InGaZnO4,LaAlO3 and SrTiO3 heterostructures explained by interface-induced gap states. J. Mater. Sci.: Mater. Electron. 29, 19607–19613 (2018). https://doi.org/10.1007/s10854-018-0161-3.Google Scholar
53.Anderson, R.L.: Experiments on Ge-GaAs heterojunctions. Solid-State Electron. 5, 341–351 (1962).Google Scholar
54.Mott, N.F.: Note on the contact between a metal and an insulator or semi-conductor. Proc. Cambridge Philos. Soc. 34, 568–572 (1938).Google Scholar
55.Fares, C., Ren, F., Lambers, E., Hays, D.C., Gila, B.P., and Pearton, S.J.: Band alignment of atomic layer deposited SiO2 on (010) (Al0.14Ga0.86)2O3. J. Vac. Sci. Technol. B 36, 061207 (2018).Google Scholar
56.Carey, P.H., Ren, F., Hays, D.C., Gila, B.P., Pearton, S.J., Jang, S., and Kuramata, A.: Conduction and valence band offsets of LaAl2O3 with (−201) β-Ga2O3. J. Vac. Sci. Technol. B. 35, 041201 (2017), https://doi.org/10.1116/1.4984097.Google Scholar
57.Carey, P., Ren, F., Hays, D.C., Gila, B.P., Pearton, S.J., Jang, S., and Kuramata, A.: Band alignment of atomic layer deposited SiO2 and HfSiO4 with (−201) β-Ga2O3. Jpn. J. Appl. Phys. 56, 071101 (2017). https://doi.org/10.7567/JJAP.56.071101.Google Scholar
58.Carey, P., Ren, F., Hays, D.C., Gila, B.P., Pearton, S.J., Jang, S., and Kuramata, A.: Band alignment of Al2O3 With (−201) β-Ga2O3. Vacuum 142, 52 (2017), https://doi.org/10.1016/j.vacuum.2017.05.006.Google Scholar
59.Hays, D.C., Gila, B.P., Pearton, S.J., and Ren, F.: Energy band offsets of dielectrics on InGaZnO4. Appl. Phys. Rev. 4, 021301 (2017), https://doi.org/10.1063/1.4980153.Google Scholar
60.Fares, C., Ren, F., Lambers, E., Hayes, D.C., Gila, B.P., and Pearton, S.J.: Band offsets for atomic layer deposited HfSiO4 on (Al0.14Ga0.86)2O3. ECS J.Solid State Sci. Technol. 7, P519 (2018).Google Scholar
61.Ghosh, K. and Singisetti, U.: Calculation of electron impact ionization coefficient in β-Ga2O3, 72nd Device Research Conference (2014), pp. 71–72.Google Scholar
62.Yang, J.C., Ahn, S., Ren, F., Pearton, S.J., Jang, S., Kim, J., and Kuramata, A.: High reverse breakdown voltage Schottky rectifiers without edge termination on Ga2O. Appl. Phys. Lett. 110, 192101 (2017).Google Scholar
63.Yang, J.C., Ren, F., Tadjer, M., Pearton, S.J., and Kuramata, A.: 2300 V reverse breakdown voltage Ga2O3 Schottky rectifiers. ECS J. Solid State Sci. Technol. 7, P92–P97 (2017).Google Scholar
64.Yang, J., Ahn, S., Ren, F., Pearton, S.J., and Kuramata, A.: High breakdown voltage (−201) β-Ga2O3 Schottky rectifiers. IEEE Electron Dev. Lett. 38, 906–909 (2017).Google Scholar
65.Cao, L., Wang, W., Harden, G., Ye, H., Stillwell, R., Hoffman, A.J., and Fay, P.: Experimental characterization of impact ionization coefficients for electrons and holes in GaN grown on bulk GaN substrates. Appl. Phys. Lett. 112, 262103 (2018).Google Scholar
66.McKay, K.G. and McAfee, K.B.: Electron multiplication in Si and Ge. Phys. Rev. 91, 1079 (1953).Google Scholar
67.McKay, K.G.: Avalanche breakdown in Si. Phys. Rev. 94, 877 (1954).Google Scholar
68.Chynoweth, A.G. and McKay, K.G.: Threshold energy for electron-hole pair production by electrons in Si. Phys. Rev. 108, 29 (1957).Google Scholar
69.Chynoweth, A.G.: Ionization rates for electrons and holes in Si. Phys. Rev. 109, 1537 (1958).Google Scholar
70.Chynoweth, A.G. and Pearson, G.L.: Effect of dislocations on breakdown in Si p-n junctions. J. Appl. Phys. 29, 1103 (1958).Google Scholar
71.Grundmann, M., Klüpfel, F., Karsthof, R., Schlupp, P., Schein, F., Splith, D., Yang, C., Bitter, S., and von Wenckstern, H.: Oxide bipolar electronics: materials, devices and circuits. J. Phys. D: Appl. Phys. 49, 213001 (2016).Google Scholar
72.Gao, S., Wu, Y., Kang, R., and Huang, H.: Nanogrinding induced surface and deformation mechanism of single crystal β-Ga2O3. Mat. Sci. Semicon. Proc. 79, 165–170 (2018).Google Scholar
73.Wu, Y.Q., Gao, S., and Huang, H.: The deformation pattern of single crystal β-Ga2O3 under nanoindentation. Materials Sci. Semicon. Proc. 71, 321–325 (2017).Google Scholar
74.Oshima, T., Hashiguchi, A., Moribayashi, T., Koshi, K., Sasaki, K., Kuramata, A., Ueda, O., Oishi, T., and Kasu, M.: Electrical properties of Schottky barrier diodes fabricated on (001) β-Ga2O3 substrates with crystal defects. Jpn. J. Appl. Phys. 56, 086501 (2017).Google Scholar
75.Nakai, K., Nagai, T., Noami, K., and Futagi, T.: Characterization of defects in β-Ga2O single crystals. Jpn. J. Appl. Phys. 54, 015201 (2015).Google Scholar
76.Kasu, M., Oshima, T., Hanada, K., Moribayashi, T., Hashiguchi, A., Oishi, T., Koshi, K., Sasaki, K., Kuramata, A., and Ueda, O.: Crystal defects observed by the etch-pit method and their effects on Schottky-barrier-diode characteristics on β-Ga2O3. Jpn. J. Appl. Phys. 56, 091101 (2017) https://doi.org/10.7567/JJAP.56.091101.Google Scholar
77.Varley, J.B., Peelaers, H., Janotti, A., and Van de Walle, C.G.: Hydrogenated cation vacancies in semiconducting oxides. J. Phys.: Condens. Matter 23, 334212 (2011).Google Scholar
78.Lany, S.: Defect phase diagram for doping of Ga2O3. APL Mater. 6, 046103 (2018).Google Scholar
79.Ohira, S., and Arai, N.: Wet chemical etching behavior of β-Ga2O3 single crystal. Phys. Status Solidi. C 9, 3116–3118 (2008).Google Scholar
80.Hu, Z., Nomoto, K., Li, W., Zhang, Z., Tanen, N., Thieu, Q.T., Sasaki, K., Kuramata, A., Nakamura, T., Jena, D., and Xing, H.G.: Breakdown mechanism in 1 kA/cm2 and 960 V E-mode β-Ga2O3 vertical transistors. Appl. Phys. Lett. 113, 122103 (2018).Google Scholar
81.Tadjer, M.J.: Cheap ultra-wide bandgap power electronics? gallium oxide may hold the answer. ECS Interface 27, 49–52 (2018). https://doi.org/10.1149/2.F05184if.Google Scholar