Carrier cooling and Auger heating in Si doped InN thin films

Silicon doped InN thin films grown on sapphire substrates by plasma-assisted molecular beam epitaxy have been studied using time-resolved photoluminescence (TRPL) upconversion technique. The back ground carrier densities vary from 6.2$\times $10$^{18}$ to 1.27$\times $10$^{20}$ cm$^{-3}$. The carrier temperature curves, derived from the TRPL at different time delay, indicate that the hot carriers lost most of their excess energy within the first 10 ps after photoexcitaiton. For low doping densities, the carrier cooling curves can be explained by carriers releasing excessive energy through the carrier--LO-phonon interaction. The extracted effective phonon emission times decreased as the photoexcited carrier concentration reduced. The radiative and nonradiative decay rates were obtained with the TRPL signals and the nonlinear dependence of the PL intensity on the carrier concentration. The derived radiative recombination rates were consistent with the theoretical predications. The Auger recombination was found to increase with the doping concentration. The reduced carrier cooling rates for large doping densities can be accounted for by the Auger heating occurred during carrier relaxation.