Raman scattering study of anharmonic phonon decay in InN

We present Raman scattering measurements on wurtzite InN over a temperature range from 80 to 660 K. To investigate all phonon modes of the wurtzite structure, measurements were performed on c and m faces of high-quality InN epilayers. High-resolution measurements of the low-frequency E-2 mode reveal a slight anharmonic broadening of such a long-lived phonon due to up-conversion processes and a substantial contribution of background impurity broadening in the determination of its linewidth. An analysis of the anharmonicity and lifetimes of the InN phonons is carried out. Possible decay channels including up-conversion processes and four-phonon processes are discussed on the basis of density functional theory calculations.