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

Raman studies are reported for the A1 TO , E1 TO , E2 2, and A1 LO symmetry phonons of AlN from 20 to 375 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 , E1 TO , and E2 2 vibrations are described by symmetric two-phonon decay. The A1 LO band is interpreted by an asymmetric two-phonon decay. Phonon lifetimes are obtained based on the observed linewidths and the dependence allows us to estimate the impurity-related phonon lifetime for each vibration. The latter ranges from 2.9 to 9.1 ps.