Strain relaxation in InAs/GaAs(111)A hetero-epitaxial structures was studied at the atomic scale by means of scanning tunnelling microscopy. The early stages of relaxation involved the formation of misfit dislocations at the boundaries of coalescing strained islands. The misfit dislocations formed a trigonal network, with an anisotropy with respect to [1¯10] and [¯110], and maintained the 3-fold rotational symmetry of the (111)A surface. No 3-dimensional growth was observed; even when beyond the critical layer thickness. The atomic displacements around the threading segments, and the strain fields which were produced by the misfit dislocations, were studied. The measured density of the misfit dislocations indicated that the strain was not fully relaxed at the critical layer thickness. The strain was gradually relieved with increasing InAs thickness, and no 3-dimensional islands were formed.

H.Yamaguchi, J.G.Belk, X.M.Zhang, J.L.Sudijono, M.R.Fahy, T.S.Jones, D.W.Pashley, B.A.Joyce: Physical Review B, 1997, 55[3], 1337-40