Strain in Epitaxial Si/SiGe Graded Buffer Structures Grown on Si (100), Si (110) and Si(111): a Raman Spectroscopy Study

Abstract

We report preliminary results on the Raman characterization of strained-Si films pseudomorphically grown on (001), (110) and (111) SiGe virtual substrates. Because the relation between strain or stress and the Raman frequencies are complex, we first derive the strain-shift coefficients for the different substrate orientations considered in this work. Then, visible and near-UV Raman spectroscopies were used to extract the in-plane lattice parameter of the virtual substrate and the strain in the thin silicon epitaxial layers grown on top. Finally, we investigated the in-plane strain distribution in strained Si/SiGe buffer layers grown on (110) and (111) silicon substrates by Raman imaging. In-plane strain fluctuations are observed both in the epilayer and the virtual substrate for all substrate orientations.