Intensity dependence of photoluminescence in GaN thin films

We report the intensity dependence of band‐gap and midgap photoluminescence in GaN films grown by electron cyclotron resonance (ECR) microwave plasma‐assisted molecular beam epitaxy. We find that the band‐gap luminescence depends linearly while the midgap luminescence has a nonlinear dependence on the incident light intensity. These data were compared with a simple recombination model which assumes a density of recombination centers 2.2 eV below the conduction band edge. The concentration of these centers is higher in films grown at higher microwave power in the ECR plasma.