Origin of temperature dependence of exciton radiative lifetime of GaN studied by phononic-excitonic-radiative model

Abstract

It is theoretically accepted that the temperature (T) dependence of the exciton radiative lifetime is proportional to 3/2 power of the temperature. However, the various experimental temperature dependence of the exciton lifetime has been reported for samples with different crystal qualities, and it is not clear which factor of crystal quality determines the temperature dependence of the exciton radiative lifetime. We calculated the exciton radiative lifetime using the phononic-excitonic-radiative model, which is an analytical model that integrates excitons of various principal quantum numbers, free carriers, and phonons. For the components determining the crystal quality, the effects of nonradiative recombination, carrier trapping, bound excitons, exciton-polaritons, and energy-level broadening on the exciton radiative lifetime are considered. Our calculation model fits the experimental radiative lifetime roughly proportional to T3/2 in a wide range from cryogenic to room temperature and also minor deviation from the T3/2 dependence. We show that the exciton radiative lifetime reflects the effects of crystal quality, whereas conventional theories suggest that it is due to the momentum distribution of excitons.