Investigation of deep-level luminescence in In0.07Ga0.93N:Mg

Deep-level defects formed in InGaN:Mg have been investigated by photoluminescence (PL) spectroscopy. Undoped In0.07Ga0.93N exhibits strong bandedge emission at 3.05 eV. Upon Mg doping the bandedge emission quenches and a 2.45 eV green band with a full-width at half-maximum of 800 meV dominates the room temperature PL spectrum. This band is attributed to donor-acceptor pair (DAP) recombination involving Mg acceptors and nitrogen vacancy donors. A decrease in the DAP emission bandwidth and an S-shaped emission shift with increasing temperature were observed and attributed to compositional fluctuations. In order to decrease the fluctuations, InGaN:Mg epilayers with a GaN capping layer were annealed at high temperature. As a result of the fluctuation reduction a fine structure related to phonon replicas was resolved. The measured phonon energy and the Huang-Rhys factor were 105 meV and 6.3, respectively, indicating strong electron-phonon coupling is responsible for the large width of the green band. (C) 2003 Elsevier B.V. All rights reserved.