It was noted that epitaxial PbSe layers on Si(111) relaxed almost completely, due to easy dislocation glide on the main {100}<110> glide system. Threading dislocations which were introduced by thermal mismatch strains were able to move over distances of several cm, and to escape at the edges of the samples. Etch-pit densities as low as 106/cm2 were obtained in layers with a thickness, d, of 4. The etch-pit density varied as d-2, and this was attributed to the annealing step and to the high dislocation mobility. It was concluded that, by repeating such annealing treatments, threading dislocation densities that were close to zero should be possible.

P.Müller, H.Zogg, A.Fach, J.John, C.Paglino, A.N.Tiwari, M.Krejci, G.Kostorz: Physical Review Letters, 1997, 78[15], 3007-10