Effect of phononic and electron collisional interaction on temperature dependent exciton radiation dynamics of doped GaN

In ultraviolet light emission devices, excitons are a high-efficiency emission source. However, the mechanism of experimentally observed dependence of excitonic radiative lifetimes on temperature (T) has not been discovered. We present a numerical simulation based on the phonon-exciton-radiation system, which reveals that the dependence of the radiative lifetime of GaN excitons on T is dominated by the population distribution among discrete and continuum energy states. This finding is in contrast to an existing model considering the existence of 1S exciton only. This population distribution is determined by the temperature-dependent integrated effect of background carrier density and exciton energy broadening, which induces a combination of high-order excitonic states and the continuum. Various experimental results on the dependence on temperature, including the functions of T3/2 and higher or lower power of T, are interpreted by a model integrating the interactions with the electron and phononic fields. The proposed model elucidates the corresponding effects of electronic and phononic processes in this complex system and provides a platform for the discussion of Wannier exciton dynamics under various thermal conditions, including nonequilibrium cases beyond the Saha-Boltzmann relation in population distribution. •We clarify the mechanism dominating temperature dependence of radiative exciton lifetime of GaN for UV emission.•All energy species including phonon are considered in the theoretical model.•Straightforward reflection of the 1S-exciton momentum distribution is restricted.•Combined effect of background electrons and energy broadening is dominant.•Thermal nonequilibrium analysis reveals asymmetric effects of electron and phonon processes.