Strain, composition and crystalline perfection in thin SiGe layers studied by Raman spectroscopy

Micro-Raman spectroscopy has been employed for measurements of Ge content and strain-relaxation of thin (< 100nm) Si1−xGex (0.2 < x < 0.35) epitaxial layers grown by molecular beam epitaxy. The phonon line width of both Raman bands, Si–Si, and Si–Ge, was studied in order to determine the crystalline quality of the SiGe layers. The dependence of Si–Si and SiGe line width on Ge content in samples obtained under a variety of growth conditions was also analysed. For the majority of samples studied in this work the phonon line width of both Si–Si and Si–Ge modes increases with decreasing temperature in the very low-temperature regime.