The role of vacancies in the red luminescence from Mg-doped GaN

The red (1.8 eV) photoluminescence (PL) band often observed in Mg‐doped GaN has been suggested to be due to a recombination process involving vacancy‐related deep defects. To identify the defects concerned, optically‐detected magnetic resonance (ODMR) and positron annihilation spectroscopy (PAS) experiments have been combined. A correlation between the PL spectra, the ODMR signals and the PAS data has been observed in as‐grown layers as the magnesium doping level is increased. The experiments provide strong evidence that the origin of the red PL is recombination of electrons from both shallow and deep donors with holes at deep acceptors, the deep donors being complexes formed from nitrogen vacancies associated with substitutional magnesium ions and the deep acceptors being gallium vacancies or related centers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)