Temperature dependence of Raman-active modes in AlN

Abstract

Micro-Raman scattering and FT-IR reflectivity measurements were performed on bulk wurtzite AlN crystals grown by PVT method over a temperature range from 10 K to the room temperature after identifying the symmetry of each of the Raman-active zone-center optic modes. The empirical relationship previously introduced for diamond for the temperature dependence of the frequency was verified on AlN. The damping of the Raman-active zone-center optic modes was measured in the same temperature range. The experimentally obtained damping is modeled by a theory taking into account a symmetric decay of the optical phonons into two and three phonons of lower energy. The results show that the decay into two phonons is the most probable channel for the Raman-active zone-center optic modes A 1(LO), E 1(TO), E 2 2(high frequency), and A 1(TO). A comparison between the temperature dependence of the phonons of AlN and other III-Nitride (GaN) was made.