Photoluminescence (PL) spectroscopy has been used to investigate the effect that annealing temperature and ambient has on annealed molecular beam epitaxy grown GaN. Significant differences induced by the different annealing conditions occur in the PL spectra in the 3.424 eV region as well as the deep level band (2.0-3.0 eV). Power resolved measurements indicate that the 3.424 eV emission is a donor-acceptor pair transition. In the deep level region peaks are observed in all spectra at 2.3 and 2.6 eV. This suggests that the 2.3 and 2.6 eV peaks are related and a model is proposed to explain this luminescence. (C) 2001 American Institute of Physics.