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

摘要

We report positron annihilation results on vacancy defects in Si-doped Al_(0 90)Ga_(0 10)N 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 × 10~(16) cm~(-3) to 2 × 10~(18) cm~(-3) in samples with a high C content, strongly correlated with the Si doping level in the samples ranging from 1 × 10~(17) cm~(-3) to 7 × 10~(18) cm~(-3). On the other hand, we find predominantly neutral cation vacancies with concentrations above 5 × 10~(18) 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.