Strain and composition in self-assembled SiGe islands by Raman spectroscopy

We have investigated self-assembled ${\mathrm{Si}}_{\text{1−x}}{\mathrm{Ge}}_x$ islands grown on Si (001). We show that the average composition and both the ${\epsilon }_{\mathrm{xx}}$ and ${\epsilon }_{\mathrm{zz}}$ average strain components can be derived from Raman scattering spectra. Both nm-sized and μm-sized islands are investigated. The experimental results are compared successfully with finite-element strain simulations. Raman scattering is shown to be a versatile and reliable tool for investigating capped and uncapped islands. It is shown that strain profiles in μm-sized islands can be obtained by means of micro-Raman.