Anharmonic decay of high-frequency LA modes in quasi-isotropic III-nitrides

We report for the first time an estimation of the spontaneous decay rates at room temperature in a selection of nitride-based nanostructures that are quasi-isotropic. We numerically calculate the phonon distribution functions and the decay rates and find that the decay channel LA → TA + TA dominates over the decay channel LA → LA + TA, which confirms Klemens' prediction [1] that LA phonon will primarily split into two doubly degenerate TA phonons through a greater variety of decay channels compared to the decay of LA into two modes, one belonging to the longitudinal acoustic and the other to the transverse acoustic branch.