Abstract

Abstract The effects of SiO 2 cap annealing at 800 °C on Ga-polar n-type and p-type GaN (0001) surfaces were compared by X-ray photoelectron spectroscopy. We found that the native oxide thickness at the GaN surfaces is usually at the monolayer level regardless of the process step, except immediately after SiO 2 cap annealing for p-type GaN. Furthermore, for both conduction types, the surface Fermi level is located between the conduction band edge and the charge neutrality level regardless of the process step, which indicated that donor-like defects existed in the vicinity of the p-type GaN surfaces.