Raman scattering analysis of relaxed Ge_xSi_1-x alloy layers

We have used Raman scattering to evaluate thick epitaxial Ge xSi1-x layers with 0.20≤x≤0.43 grown on Si (100) substrates. We show that a detailed consideration of the composition dependencies of the relative intensities of the various phonon modes can enhance the sensitivity of Raman scattering to variations in composition and strain. We find that samples are uniform on a scale of ≅1 μm laterally and <1000 Å in the growth direction.