Multiphonon resonant Raman scattering in non-polar GaN epilayers

Multiphonon resonant Raman scattering in non-polar a-plane (11 (2) over bar0) GaN epitaxial layers grown on sapphire substrate were investigated. We report longitudinal optical phonon overtones up to seventh order in a-plane GaN epilayer, which has rarely been observed earlier in GaN. However, for high quality polar c-plane (0001) GaN epilayer and semi-polar r-plane (11 (2) over bar2) GaN epilayer, resonant Raman spectra were not very prominent. Strong multiphonon resonant Raman scattering process is explained by exciton-mediated multiphonon Raman scattering and defect-induced Frohlich interaction. (C) 2014 AIP Publishing LLC.