Temperature dependence of the radiative lifetime in GaN

Using time-resolved photoluminescence spectroscopy, we determine the temper ature dependence of the radiative lifetime for GaN layers with doping level s from 10(16) to 10(18) cm(-3). The experimental results are analyzed by a coupled rate-equation model taking into account band-to-band, free and boun d excitons, as well as donor-to-band recombination. An analytic expression for the radiative lifetime of this coupled system is derived and fit to the data. Over the entire temperature range, radiative recombination is strong ly affected by the decay of either bound or free excitons. The temperature dependence and the absolute values for the radiative lifetime are governed by the coupling between the individual populations. This coupling in turn i s determined by the binding energies of the respective species. Using a bin ding energy of 26.4 meV for the free exciton, we obtain best-fit values of 30+/-6 and 36.3+/-2 meV for the donor and the donor-bound exciton, respecti vely. [S0163-1829(98)50638-0].