Femtosecond time-resolved photoreflectance of InN thin films.*

The kinetics of the nonequilibrium photoexcited carriers in high-quality InN is investigated using femtosecond time-resolved pump-probe reflectivity measurements at room temperature. We observed that both of the hot-carriers relaxation times and carrier recombination times decrease with increasing photoexcited carrier density. We attribute the hot-carriers relaxation times anomaly is caused by the impact-ionization effect. And the carrier density-dependent recombination times can be explained by the Auger recombination (AR). The AR rate was found to have a quadratic rather than a cubic dependence on carrier density. The experimental results allowed the coefficients for impact-ionization, AR and a defect capture time in InN to be estimated as 2.3x10$^{-9}$cm$^{3}$/s, 2.5x10$^{-10}$cm$^{3}$/s and 535 ps, respectively.