Defects in nitride semiconductors as seen by positrons

Positron annihilation spectroscopy is a powerful set of methods for the detection, identification and quantification of vacancy-type defects in semiconductors. In the past decades, it has been used to reveal the relationship between the (opto-)electronic properties and specific defects in a wide variety of elemental and compound semiconductors, including nitrides. In binary compounds, the selective sensitivity of the technique is rather strongly limited to cation vacancies that possess significant open volume and suitable charge: negative of neutral. The focus of this paper is in the recent advances in combining state-of-the-art positron annihilation experiments and ab initio computational approaches in identifying and quantifying defects in AlGaN alloys and GaN/AlGaN device structures.