𝛽-Ga2O3 has recently received attention as an ultra-wide-band-gap material, promising as transparent conductor and for high-power device applications. In this talk, we review some recent computational work on the electronic band structure and it defects. The electronic band structure was calculated using the quasiparticle self-consistent GW method including a correction of the screened Coulomb interaction W for electron-hole interaction and lattice-polarization effect. The selection rules of the optical transition help understand the anisotropy of the optical absorption.1 Among the point defects, which have already been discussed in various papers,2 we here focus on the two types of Ga–vacancies, which can
occur on both the tetrahedral and octahedral Ga site. Electron paramagnetic resonance (EPR) related to the Ga-vacancy has been reported.3,4 Here we present first-principles calculations of the g-factor and hyperfine structure, which allow us to identify the EPR spectrum observed after high energy particle irradiation, with the tetrahedral Ga vacancy in the 2- charge state. Modification of the EPR spectrum under low temperature photoexcitation are explained by the following model. The EPR spectrum of the tetrahedral Ga vacancy shows superhyperfine interaction with two Ga atoms which are nearest neighbors to the oxygen on which the defect localizes in the q=2- charge state. The g-tensor has its largest deviation from the free-electron value for the crystallographic b-direction in which the defect Ga-O-Ga complex is oriented. According to Ref. 2, the tetrahedral Ga vacancy has its 2-/3- transition level closer to the conduction band minimum than the octahedral one. Upon illumination, this defect may become inactivated while the octahedral one is activated. The latter has a different orientation of its main largest g-tensor component but similar superhyperfine splitting with two Ga atoms. These computational findings explain the corresponding experimental observations.
1 Amol Ratnaparkhe and Walter R. L. Lambrecht, Appl. Phys. Lett. 110, 132103 (2017)
2 Peter Déak, Quoc Duy Ho, Florian Seemann, Bálint Aradi, Michael Lorke, and Thomas Frauenheim,
Phys. Rev. B 95, 075208 (2017) and references therein.
3 B. E. Kananen , L. E. Halliburton , K. T. Stevens , G. K. Foundos , and N. C. Giles, Appl. Phys. Lett. 110, 202104 (2017)
4 H.Jürgen von Bardeleben, unpublished
Walter R. L. Lambrecht, Dmitry Skachkov, Amol Ratnaparkhe, Hans Jürgen von Bardeleben, Uwe Gerstmann, Quoc Duy Ho, and Peter Déak, "Computational studies of beta-Ga2O3 band structure and the electron paramagnetic resonance spectra of the Ga-vacancy defects (Conference Presentation)," Proc. SPIE 10533, Oxide-based Materials and Devices IX, 1053304 (Presented at SPIE OPTO: January 28, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2297411.5751529232001.
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