OPTICAL ANISOTROPY OF SI GE SUPERLATTICES - RESONANT RAMAN-SCATTERINGIN INPLANE GEOMETRY/

Using a micro-Raman setup, we performed a systematic resonant Raman sc attering study on short-period (Si)(n)(Ge)(n) superlattices (n = 4-12) in in-plane geometry from polished sample edges. Due to the confineme nt of optical phonon modes electronic states in Si and Ge layers can b e probed separately. The Raman efficiencies measured between 1.7eV and 2.6eV for parallel and crossed polarization are compared with calcula tions of the dielectric function decomposed into contributions of Si a nd Ge atoms. A pronounced polarization dependence of the Raman cross s ection is found in qualitatively good agreement with theory. For polar ization 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 t he layers.