Decay of zone-center phonons in GaN with A1, E1, and E2 symmetries

We report Raman studies of the A1 TO , E1 TO , E2 2, A1 LO , and E1 LO symmetry phonons of GaN from 20 to 325 K. By applying anharmonic decay theory to the observed temperature dependences of the phonon energies and linewidths, we determine the phonon decay mechanisms of these zone-center vibrations. Thermal expansion is taken into account using published temperature-dependent coefficients. The A1 TO and E1 TO vibrations are described by symmetric two-phonon decay. The E2 2 decays via the creation of three phonons. Both A1 LO and E1 LO bands are interpreted by an asymmetric two-phonon decay, with a minor contribution to the decay of the former from the three-phonon creation. Phonon lifetimes are obtained based on the observed linewidths