Crystallographic Orientations and Interfacial Mismatches of Single-Crystal CdS Films Deposited on Various Faces of Zinc-Blende-Type Materials

Single-crystal CdS (wurtzite-type) layers were prepared by vapor growth technique on the (001), (110), (112), and (221) faces of zinc-blende-type crystals such as GaP, GaAs, InAs, and CdTe in hydrogen atmosphere. Deposition temperatures were ranging from 620 to 740°C. The layer thicknesses were up to 20 μm. Relations of crystallographic orientation between the grown layers of CdS and the substrates were studied. It was found that (1) the [0001] a axis of CdS was nearly parallel to the [111] a axis of the substrate and (2) the (112̄0) face of CdS deposited on the faces except for (112) was parallel to the (11̄0) face of the substrate, and the (112̄0) face of CdS deposited on the (112) face was not always parallel to the (11̄0) face. Angles between the [0001] a and [111] a axes were a few degrees (up to 3°) and they depended both on substrate materials and orientations of the substrate surfaces. The dislocation model of small-angle grain boundaries was applied to interpret the result. It was found that CdS crystals are grown on crystallographic planes of zinc-blende-type materials in such a way that the interfacial mismatch between close-packed planes of CdS and the substrates vanishes.