Photoluminescence dynamics of exciton-exciton scattering in a lightly alloyed InGaN thin film

We have investigated the photoluminescence (PL) dynamics of a lightly alloyed In(0.02)Ga(0.98)N thin film under intense excitation conditions at 10 K. In the In(0.02)Ga(0.98)N thin film, a PL band due to exciton-exciton scattering, the so-called P band, appears with a thresholdlike nature in the excitation-power region higher than similar to 3 mu J/cm(2). Under the condition that the exciton-exciton scattering occurs, the PL-decay profile consists of a fast decay component of the P band (of the order of 10 ps) and a slow decay component of a localized exciton band. The decay time of the P band gradually shortens with increasing excitation power. The change in the decay time can be explained qualitatively by the photon-like characteristics of the lower polariton branch that is the final state of the P emission. Furthermore, we have clearly observed the temporal change in the peak energy of the P band, which reflects an effective temperature of the excitonic system. The energy shift of the P band suggests that the P emission process reaches equilibrium with the lattice temperature after similar to 100 ps.