The red (1.8eV) photoluminescence band often observed in Mg-doped GaN was suggested to be due to a recombination process involving vacancy-related deep defects. To identify the defects concerned, optically-detected magnetic resonance and positron annihilation spectroscopy experiments were combined. A correlation between the photoluminescence spectra, the optically-detected magnetic resonance signals and the positron annihilation spectroscopy data was observed in as-grown layers as the Mg doping level was increased. The experiments provided strong evidence that the origin of the red photoluminescence was recombination of electrons from both shallow and deep donors with holes at deep acceptors, the deep donors being complexes formed from N vacancies associated with substitutional magnesium ions and the deep acceptors being gallium vacancies or related centers.

The Role of Vacancies in the Red Luminescence from Mg-Doped GaN. S.Zeng, G.N.Aliev, D.Wolverson, J.J.Davies, S.J.Bingham, D.A.Abdulmalik, P.G.Coleman, T.Wang, P.J.Parbrook: Physica Status Solidi C, 2006, 3[6], 1919–22