Reduction of Threading Dislocation Densities in Heavily Lattice Mismatched PbSe on Si(111) by Glide

Epitaxial PbSe layers on Si(111) relax nearly completely owing to the easy dislocation glide in the main ${100}〈110〉$ glide system. Threading dislocations introduced by the thermal mismatch strains are able to move distances of several cm and to escape at the edges of the samples. Etch-pit densities as low as ${10}^{6}\phantom{\rule{0ex}{0ex}}\mathrm{cm}{}^{\ensuremath{-}2}$ were obtained in layers with a thickness of $d\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4\phantom{\rule{0ex}{0ex}}\ensuremath{\mu}\mathrm{m}$. The etch-pit density scales with ${1/d}^{2}$, which may be understood as a consequence of the annealing step and of the high mobility of dislocations. By applying several anneal cycles, threading dislocation densities of essentially zero should result.