Vacancy defects in III-nitrides: what does positron annihilation spectroscopy reveal?

Abstract

The purpose of this paper is to present a short review and comparison of the results obtained with positron annihilation spectroscopy studies of vacancy defects in AlN, GaN and InN. The combination of positron lifetime and Doppler broadening techniques with theoretical calculations has provided the means to deduce both the identities and the concentrations of the vacancies in these materials, while performing measurements as a function of temperature has given information on the charge states of the detected defects. The III-sublattice vacancies are common defects in all the III-nitrides, and they compensate donors either by forming vacancy-impurity complexes or by providing deep states for electrons. In some cases, N vacancies have also been observed.