Spectroscopic ellipsometry and X-ray diffraction studies on Si1-xGex/Si epifilms and superlattices

Abstract Comprehensive optical and structural properties are reported on several MBE grown thin Si 1-x Ge x epifilms and Si 1-x Ge x /Si superlattices with low Ge contents by using spectroscopic ellipsometry (SE), high resolution x-ray diffraction (HR-XRD) and Raman scattering (RS). For thin Si 1-x Ge x films, our appraised results of the optical dielectric functions from SE spectra fitted to the parameterized models have revealed discrepancies with the existing data. While E 1 and E 1  + Δ 1 critical point energies have shown similarities, their amplitudes uncovered ∼25% larger value for the E 1 band-edge, and ∼10% larger value for the E 1  + Δ 1 band-edge. In our samples, the observed vibrational peaks in the RS are classified as unstrained Si Si, Ge Ge and Ge Si modes. These mode assignments in Si 1-x Ge x alloys are evaluated compared and discussed with the available RS data.