Optical anisotropy of [formula omitted] superlattices: Resonant Raman scattering in in-plane geometry

Abstract

Using a micro-Raman setup, we performed a systematic resonant Raman scattering study on short-period (Si) n (Ge) n superlattices ( n = 4–12) in in-plane geometry from polished sample edges. Due to the confinement of optical phonon modes electronic states in Si and Ge layers can be probed separately. The Raman efficiencies measured between 1.7 eV and 2.6 eV for parallel and crossed polarization are compared with calculations of the dielectric function decomposed into contributions of Si and Ge atoms. A pronounced polarization dependence of the Raman cross section is found in qualitatively good agreement with theory. For polarization of the light parallel to the layers strong transitions around 2.2 eV localized in the Ge layers are observed. These transitions are considerably weakened for polarization of the light perpendicular to the layers.