Phonon lifetimes in bulk AlN and their temperature dependence

We report on the Raman analysis of the phonon lifetimes of the A1(LO) (longitudinal optical) and E2(high) phonons in bulk AlN crystals and their temperature dependence from 10 to 1275 K. Our experimental results show that amongst the various possible decay channels, the A1(LO) phonons decay primarily into two phonons of equal energy (Klemens model), most likely longitudinal-acoustic phonons, whereas the E2(high) phonon decays asymmetrically into a high-energy and a low-energy phonon. Possible decay channels of the E2(high) phonon have been shown to include combinations of E2(low) and acoustic phonons. Phonon lifetimes of the A1(LO) phonon and the E2(high) phonon of 0.75 and 2.9 ps, respectively, were measured at 10 K.