The spontaneous formation of a Ga-oxide (GaO x ) intermediate layer at the GaN/SiO 2 interface has been reported during the SiO 2 deposition on the GaN substrate. In this study, we have performed first-principles calculations and unveiled atomic and electronic structures of the GaN/SiO 2 interface with 1-nm thick GaO x intermediate layer. Our calculations show that the top-layer Ga atoms on the GaN side are terminated with the O atoms on the GaO x side, leading to the clean GaN/GaO x interface and the absence of the electronic state in the midgap region. However, strongly localized states, which are originated from O atoms lone-pair orbitals in the –GaOSi– local structures, emerge in the gap near the valence-band maximum of GaN. These in-gap states become hole traps in GaN MOS devices, leading to a degradation in device controllability and operational speed. [ABSTRACT FROM AUTHOR]

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