Subpicosecond time-resolved Raman studies of non-equilibrium excitations in wide bandgap GaN

Non-equilibrium phonon dynamics in wurtzite GaN have been studied by subpicosecond time-resolved Raman spectroscopy. The population relaxation time of longitudinal optical phonons was directly measured to be τ ≅ (5 ± 1) ps at T = 25 K. The experimental results on the temperature dependence of the lifetime of longitudinal optical phonons suggest that the primary decay channels for these phonons are the decay into (i) one transverse optical phonon and one high energy, longitudinal or transverse acoustical phonons; and (ii) one transverse optical phonon and one E₂ phonon.