SiGe/Si layers-early stages of plastic relaxation

The plastic relaxation of SiGe/Si is closely related to the nucleation of misfit dislocations at early stages. We have investigated the very early stages at annealing temperatures ranging from 520degreesC to 670degreesC by means of x-ray topography (XRT), atomic force microscopy (AFM) and transmission electron microscopy. At misfit dislocation densities within the range accessible by XRT, i.e. up to about 1000cm(-1), dislocations bundles predominate. This is verified by AFM and is explained by heterogeneous nucleation. The fewer the dislocations that are contained within dislocation bundles the rarer the blocking and cross slip that are observed. It is demonstrated that laser heating increases the number of nucleation centres drastically and is well suited to induce nucleation at selected sites. Furthermore, these nucleation centres provide dislocation bundles containing only a few dislocations. In contrast to this, implantation can produce defects that stop dislocation propagation quite effectively at the comparatively low temperatures used in our experiments.