Strain relaxation of faceted Ge islands on Si(113)

We studied the formation and strain relaxation of Ge islands on Si(113) grown at 700°C by molecular beam epitaxy. Atomic force microscopy reveals that they are mainly (113) top faceted and show a mesa-like shape. Initially formed Ge islands tend to elongate along [332] due to their anisotropic shear strain. With increasing Ge coverage, they grow mainly laterally towards particular directions, forming large V-shaped Ge clusters. This is analyzed to be caused by the formation of {111} slide plane-associated dislocations. The dislocations are shown to be localized in the islands. Considerable Si material has diffused into the Ge islands. Strain and Ge content in the islands are quantitatively analyzed by micro-Raman spectroscopy.