We have employed the photoluminescence (PL) and surface photovoltage spectroscopy (SPS) measurements to study the effects of (NH4)2Sx treatment on the optical and electrical properties of p-type GaN (p-GaN) in this study. From the PL and SPS measurements, it is suggested that the (MgGa–VN)2+ (MgGa:Ga vacancies occupied by Mg; VN:nitrogen vacancies) complexes near the p-GaN surface region were transformed into the (MgGa-SN)0 (SN:N vacancies occupied by S) complexes after (NH4)2Sx treatment, which resulted in the reduction of the ∼ 2.8-eV PL intensity and the increase of the hole concentration near the p-GaN surface region.
