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 r greater than or equal to 5 X 10(17) 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 tau congruent to 5 +/- 1 ps at T = 25 K. (C) 1996 American Institute of Physics.