Deep-level defects in InGaN:Mg were investigated by photoluminescence spectroscopy. Undoped In0.07Ga0.93N exhibited a strong bandedge emission at 3.05eV. Upon Mg doping, the bandedge emission was quenched and a 2.45eV green band with a full-width at half-maximum of 0.80eV dominated the room-temperature photoluminescence spectrum. This band was attributed to donor–acceptor pair recombination involving Mg acceptors and N vacancy donors. A decrease in the donor–acceptor pair emission bandwidth and an S-shaped emission shift with increasing temperature were observed and were attributed to compositional fluctuations. In order to decrease the fluctuations, InGaN:Mg epilayers with a GaN capping layer were annealed at high temperatures. 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 0.105eV and 6.3, respectively, indicating that strong electron–phonon coupling was responsible for the large width of the green band.

Investigation of Deep-Level Luminescence in In0.07Ga0.93N:Mg. B.Han, M.P.Ulmer, B.W.Wessels: Physica B, 2003, 340-342, 470-4