Strain relaxation of patterned Ge and SiGe layers on Si(001) substrates

We have investigated dislocation morphology and strain relaxation mechanisms of SiGe and Ge sub-micron wide striped mesa lines patterned on Si(0 0 1) substrates. The patterning of SiGe and Ge layers principally leads to asymmetric elastic strain relaxation. Post-patterning anneal induces 60 degrees dislocation introduction to relax the strain but the narrower the line width the more dominant is the elastic strain relaxation. In the case of 250 nm wide SiGe lines, 60 degrees dislocation introduction along the line is critically suppressed so that asymmetric strain distribution is realized. On the other hand, for the Ge line structure, pre-formed pure edge dislocations elongate along both orthogonal directions at the heterointerface independent of the line geometry even with the line width of 250 nm. Thus strain relaxation occurs symmetrically and rigidly. These results can be explained by deference of the introduction and propagation mechanisms of 60 degrees and pure-edge dislocations.