The microstructures of monocrystalline ZnS thin films which had been grown epitaxially onto (100)GaAs were investigated by means of high-resolution transmission electron microscopy. The predominant defect structures were {111} stacking faults and interface mismatch dislocations. The presence of stacking faults was limited to the first 70nm of grown film, and almost no defects were observed when the thickness was greater than 100nm. The stacking faults in {111} layers could be generated at the substrate/film interface via 2 mechanisms. Firstly, a small interface angle between the substrate and the film resulted in the appearance of edge-type dislocations, due to additional (002) ZnS layers. Some of the stress which was created by these interface dislocations was relaxed by the generation of stacking faults. Secondly, mismatch dislocations with additional {111} layers, due to the lattice mismatch (4.4%) between GaAs and ZnS, also favored the formation of stacking faults at the interface.

M.Arnold, Z.L.Wang, W.Tong, B.K.Wagner, S.Schön, C.J.Summers: Philosophical Magazine A, 1997, 75[5], 1209-20