Role of edge dislocations in plastic relaxation of GeSi/Si(001) heterostructures: Dependence of introduction mechanisms on film thickness

It has been shown that, in the GeSi/Si(001) heterosystem at lattice parameter mismatches of $\sim$ 2% and more, a small critical thickness of the introduction of dislocations leads to the implementation of the mechanism of induced nucleation of misfit dislocations. This mechanism consists in that the stress field of an already existing 60$^\circ$ dislocation provokes introduction of a secondary 60$^\circ$ dislocation with an opposite-sign screw component. As a result of the interaction of such dislocation pairs, edge misfit dislocations are formed, which do control the plastic relaxation process. This mechanism is most efficient when dislocations are introduced at the GeSi film thickness only slightly exceeding the critical thickness of the introduction of 60$^\circ$ dislocations, and there are threading dislocations. The dominant type of misfit dislocations (60$^\circ$ or edge) in the Ge-on-Si(001) system can be controlled by varying the mismatch parameter in the heteropair.