Second order Raman spectroscopy of the wurtzite form of GaN

Abstract

We report on Raman scattering by phonon pairs in GaN films grown on sapphire substrates by plasma-enhanced molecular beam epitaxy. The first order data are consistent with results obtained from GaN bulk crystals of the wurtzite structure. The A1 and the much weaker E2 symmetry components of the second order scattering have been identified. Two-phonon spectra are dominated by contributions due to longitudinal optical phonons.