SUBPICOSECOND TIME-RESOLVED RAMAN STUDIES OF NONEQUILIBRIUM EXCITATIONS IN WIDE BANDGAP GAN

Non-equilibrium phonon dynamics in wurtzite GaN have been studied by s ubpicosecond time-resolved Raman spectroscopy. The population relaxati on time of longitudinal optical phonons was directly measured to be ta u congruent to (5 +/- 1)ps at T = 25 K. The experimental results on th e temperature dependence of the lifetime of longitudinal optical phono ns suggest that the primary decay channels for these phonons are the d ecay into (i) one transverse optical phonon and one high energy, longi tudinal or transverse acoustical phonons, and (ii) one transverse opti cal phonon and one E-2 phonon.