A detailed analysis was made of point-defect clustering in strained Si/SiGe/(001)Si structures. This included the interaction of point defects with the strained interfaces and the sample surface during 400kV electron irradiation at room temperature. The point-defect cluster formation was very sensitive to the sign and magnitude of the strain in the Si and SiGe layers. A small (-0.3%) compressive strain in SiGe caused the aggregation of vacancies in the form of metastable [110]-oriented chains. These were located on {113} planes, and recombined with further interstitials. Tensile strains in the Si layer led to the aggregation of interstitial atoms in the form of additional [110] rows which were inserted on {113} planes, with [001]-split configurations. The chain-like configurations were characterized by a large (0.13nm) outwards lattice relaxation for interstitial rows and a very small (0.02nm) inward relaxation for vacancy chains. A compressive strain of more than -0.5% strongly depressed point-defect generation within the strained SiGe; due to the large positive formation volume of a Frenkel pair. This led to the suppression of point-defect clustering in strained SiGe, such that the latter relaxed via the diffusion of vacancies from the Si layer; thus giving rise to intermixing at the Si/SiGe interface. In material with an 0.9% misfit, a greatly increased flow of vacancies from the Si layer to the SiGe layer, and an increased biaxial strain in the SiGe, promoted the preferential aggregation of vacancies on the (001) plane. These relaxed to form intrinsic 60º dislocation loops.

In Situ HREM Irradiation Study of Point-Defect Clustering in MBE-Grown Strained SiGe/(001)Si Structures L.Fedina, O.I.Lebedev, G.Van Tendeloo, J.Van Landuyt, O.A.Mironov, F.H.C.Parker: Physical Review B, 2000, 61[15], 10336-45