Composition and structure of Ge islands grown on Si(001) and of SiGe grown on Si mesa

The thickness, the composition and the quality, of Si 1− x Ge x epilayers grown by molecular beam epitaxy on Si mesa structures, have been studied by Raman scattering. It has been shown that the layer deposited on the (001) plane of the mesa is thicker and of better quality that the one deposited on the (111) plane. Big Ge islands were grown on Si substrates, the composition of the islands vary with their size and with their thickness. In 2×2 μm and 150-nm thick islands, the Si composition varies from ≅10% at the edge of the island to ≅30% at the maximum height. In 200×200 nm and ≅30 nm height islands the Si content is ≅10%. This results points to a high surface mobility of the Si atoms on the substrate surface.