Identification of the VAl-ON defect complex in AlN single crystals

In this Rapid Communication, we report positron annihilation results on in-grown and proton irradiation-induced vacancies and their decoration in aluminium nitride (AlN) single crystals. By combining positron lifetime and coincidence Doppler measurements with ab initio calculations, we identify in-grown VAl-ON complexes in the concentration range 1018 cm-3 as the dominant form of VAl in the AlN single crystals, while isolated VAl were introduced by irradiation. Further, we identify the UV absorption feature at around 360 nm that involves V Al. © 2011 American Physical Society.