Stress and composition of C-induced Ge dots on Si(100)

Monte Carlo simulations shed light on the stress field and composition of C-induced Ge islands on Si(100). It is shown that the dots do not contain C, under any conditions of temperature and coverage, but have a gradual composition profile from SiGe at the bottom to Ge at the apex. The average compressive stress in the islands is considerably reduced compared to the pure Ge/Si case. At low Ge coverage, the top substrate layer around the dots is enriched with Si-C dimers. At high Ge contents, Ge wets the surface and covers the predeposited C geometries. We predict enhancement of Ge content in the islands upon C incorporation.