Theoretical investigations of phonon intrinsic mean-free path in zinc-blende and wurtzite AlN

Abstract

We present theoretical investigations of the anharmonic phonon mean-free path in cubic and hexagonal AlN. The cubic anharmonicity in crystal potential has been modeled within an anharmonic elastic continuum model. Numerical calculations have been carried out within the Fermi's golden rule scheme and by using the phonon dispersion and group velocity results from a full lattice dynamical model. The calculated mean-free path results for both crystal phases are compared with estimates made previously by Watari et al. [J. Mater. Res. 17, 2940 (2002)] for the hexagonal phase, and a discussion on the level of agreement is provided. Our work predicts that at room temperature and above, the average phonon mean-free path for the zinc-blende phase is approximately four times that for the wurtzite phase, suggesting that AlN will exhibit far better high thermal conductivity behavior in its cubic phase.