Nonequilibrium electron distributions and phonon dynamics in wurtzite GaN

We report experimental measurements of nonequilibrium electron distributions as well as phonon dynamics in wurtzite GaN by using subpicosecond time-resolved Raman spectroscopy. Our experimental results have demonstrated that for electron densities n≥5×1017 cm-3, the nonequilibrium electron distributions in wurtzite GaN can be very well described by Fermi-Dirac distribution functions with the temperature of electrons substantially higher than that of the lattice. The population relaxation time of longitudinal optical phonons was directly measured to be τ5±1 ps at T=25 K.