Temperature dependence of the A₁(LO) and E₂ (high) phonons in hexagonal InN nanowires

The frequencies and dampings of the zone-center optical phonon modes of A1 (LO) (longitudinal-optical) and E2 (high) in wurtzite InN nanowires have been investigated by micro-Raman scattering in the temperature range from 80 to 300 K. Our results reveal that the phonon frequencies decrease and the linewidths broaden with increasing temperature. The obtained experimental data of the frequencies and linewidths at various temperatures can be well described by an empirical model which takes into account the contribution of the thermal expansion of lattice and symmetric decay of phonons into two and three identical phonons with lower energy. The results show that decay into two phonons is the probable channel for the A1 (LO) mode and three-phonon decay dominates the E2 (high) mode.