Surface- and point-defect-related Raman scattering in wurtzite semiconductors excited above the band gap

Abstract

We present a model for exciton-mediated first-order Raman scattering by longitudinal optical phonons in the presence of surfaces and point defects. It is consistent with the experimental data for all wurtzite structure materials investigated and reviewed here (GaN, InN, ZnO and CdS) and also explains not yet understood observations in the literature. We distinguish between the involvement of elastic scattering by the surface and by point defects in the scattering process. Surface scattering causes the dependence of the line position on the crystal orientation of the excited surface in pure crystals. Point defect scattering is independent of the crystal orientation and appears as an additional contribution in defect-rich crystals. We postulate the polarization properties of these distinct processes which are in good agreement with the experiments and allow us to identify and separate the contributions of these two effects from the polarized spectra.