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

Comprehensive optical and structural properties are reported on several MBE grown thin Si1-xGex epifilms and Si1-xGex/Si superlattices with low Ge contents by using spectroscopic ellipsometry (SE), high resolution x-ray diffraction (HR-XRD) and Raman scattering (RS). For thin Si1-xGex 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 + Delta(1) critical point energies have shown similarities, their amplitudes uncovered similar to 25% larger value for the E-1 band-edge, and similar to 10% larger value for the E-1 + Delta(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 Si1-xGex alloys are evaluated compared and discussed with the available RS data. (C) 2017 Elsevier B.V. All rights reserved.