Influence of a predeposited Si1−xGex layer on the growth of self-assembled SiGe/Si(001) islands

The growth of self-assembled Ge(Si) islands on a strained Si1−xGex layer (0% < x < 20%) is studied. The size and the surface density of islands are found to increase with Ge content in the Si1−xGex layer. The increased surface density is related to augmentation of the surface roughness after deposition of the SiGe layer. The enlargement of islands is accounted for by the decrease of the wetting layer in thickness due to the additional elastic energy accumulated in the SiGe layer and to enhanced Si diffusion from the Si1−xGex layer into the islands. The increase in the fraction of the surface occupied by islands leads to a greater order in the island arrangement.