Point defects in SiGe alloys: structural guessing based on electronic transition analysis

The progress achieved in the various epitaxial-growth procedures is significant enough today to allow the addressing of new questions related to the structures at the atomic scale of various defects in alloy materials. In this review we shall focus particularly on SiGe which is miscible in all proportions. The chemical disorder, resulting from mixing-entropy constraints, offers a large distribution of atomic environments around a given point defect. In the immediate neighborhood of the defect, which we shall restrict mainly to the first two or three atomic shells, none of the existing imaging techniques can provide any reliable information. On the other hand, electronic transport techniques, based on carrier capture and emission processes turns out to be very sensitive to the local atomic environment. The highly localized character of the wavefunction of the carriers trapped at the defect links the atomic environment of the defect to the carrier properties. In this work we shall illustrate these features for some simple but technologically important point defects in relaxed SiGe and makes an inspired guess at their atomic structures.