Determination of Ge-fraction-shift coefficients for Raman spectroscopy in all vibration modes investigated by single-crystalline bulk SiGe and its application to strain evaluation in SiGe film grown on substrate

Abstract

We reported the strain-free Raman shift (ω 0) for all vibration modes (Ge–Ge, Si–Ge, and Si–Si) over the entire Ge fraction range using silicon–germanium (SiGe) single-crystals which were strain-free without boundaries and buffer/substrate layers. The determined Ge-fraction-shift coefficients varied with the Ge fraction as linear for the Si–Si and Ge–Ge vibration modes and as nonlinear for the Si–Ge mode, respectively. The Raman shifts for all vibration mode over the entire Ge fraction range were shifted to the higher wavenumber side than previous studies, implying that the strain effect reported in previous studies can be completely excluded in the present study. We applied the derived ω 0 to biaxial strain and composition evaluation in a SiGe film grown on buffer/substrate layer.