On the nature of Radiative Recombination Processes in GaN

A mechanism for efficient radiative light emission in GaN is presented. Stokes shifted emission was found to propagate almost exclusively along the c-plane when excited deep behind this surface. Onset of stimulated emission is observed. Emission intensity increases with the magnitude of the Stokes shift which in turn increases with film thickness, i.e. reduced biaxial stress conditions. We propose a model for the levels nature based on the strong oscillator of the heavy hole A-transition and its crystal field coupling to the small density of states associated the light hole B-transition. Highest emission is found for bulk-like stress conditions where the valence band top is found to be formed by the light hole mass.