Surface and interface-related phonon modes in InN/AlN nanolayer structures

We study the conditions for appearance and observation of surface and interface phonon-polariton (SPP and IPP) modes in thin InN layers grown on sapphire using AlN buffer. Theoretical dispersion relations of the IPP modes in the system air/InN/AlN/sapphire for different thickness of the InN layer are obtained. Features, additional to those due to the compounds optical phonons, are observed. The asymmetry in the experimentally observed Raman mode peaks is associated with the appearance of interface phonon-polariton excitations at wave-numbers between the TO and LO modes, which are not reported by now.