Electrical compensation and cation vacancies in Al rich Si-doped AlGaN

Abstract

We report positron annihilation results on vacancy defects in Si-doped Al0.90Ga0.10N alloys grown by metalorganic vapor phase epitaxy. By combining room temperature and temperature-dependent Doppler broadening measurements, we identify negatively charged in-grown cation vacancies in the concentration range from below 1×1016 cm−3 to 2×1018 cm−3 in samples with a high C content, strongly correlated with the Si doping level in the samples ranging from 1×1017 cm−3 to 7×1018 cm−3. On the other hand, we find predominantly neutral cation vacancies with concentrations above 5×1018 cm−3 in samples with a low C content. The cation vacancies are important as compensating centers only in material with a high C content at high Si doping levels.