Layers with Ge concentrations of up to 14% were grown, by means of liquid-phase epitaxy, onto oxide-patterned (111) Si substrates. The strains and defects were studied by using transmission electron microscopy. At Ge concentrations of less than 10%, strain relaxation occurred via the heterogeneous nucleation of dislocation loops at the edges of oxide masks. It was found that cross-slip produced pinning points from which Frank-Read sources ejected dislocations into the substrate. These dislocations relaxed the strains that were introduced by misfit and oxidation. At Ge contents above 10%, misfit dislocations were observed at the Si/SiGe interface. Only a few threading dislocations occurred and were confined to seed areas where the SiGe layer grew directly onto the Si substrate. Because the edges of the oxide mask acted as obstacles to dislocation propagation, SiGe layers which grew laterally on the oxide-covered Si substrate were almost free of dislocations.

F.Banhart, A.Gutjahr: Journal of Applied Physics, 1996, 80[11], 6223-8