No abstract

We present a detailed analysis of the point-defect clustering in strained Si/Si 1Ϫx Ge x /(001)Si structures, including the interaction of the point defects with the strained interfaces and the sample surface during 400 kV electron irradiation at room temperature. Point-defect cluster formation is very sensitive to the type and magnitude of the strain in the Si and Si 1Ϫx Ge x layers. A small compressive strain (Ϫ0.3%) in the SiGe alloy causes an aggregation of vacancies in the form of metastable ͓110͔-oriented chains. They are located on ͕113͖ planes and further recombine with interstitials. Tensile strain in the Si layer causes an aggregation of interstitial atoms in the forms of additional ͓110͔ rows which are inserted on ͕113͖ planes with ͓001͔-split configurations. The chainlike configurations are characterized by a large outward lattice relaxation for interstitial rows (0.13 Ϯ0.01 nm) and a very small inward relaxation for vacancy chains (0.02Ϯ0.01 nm). A compressive strain higher than Ϫ0.5% strongly decreases point-defect generation inside the strained SiGe alloy due to the large positive value of the formation volume of a Frenkel pair. This leads to the suppression of point-defect clustering in a strained SiGe alloy so that SiGe relaxes via a diffusion of vacancies from the Si layer, giving rise to an intermixing at the Si/SiGe interface. In material with a 0.9% misfit a strongly increased flow of vacancies from the Si layer to the SiGe layer and an increased biaxial strain in SiGe both promote the preferential aggregation of vacancies in the ͑001͒ plane, which relaxes to form intrinsic 60°dislocation loops.

No abstract

No abstract