Channeling studies of Pb1−xSnxTe/PbSeyTe1−y epitaxial structures

Channeling measurements have been carried out using MeV4He+ ions to study layers of Pb1−xSnxTe on PbSeyTe1−y, and vice versa, made using hot-wall epitaxy. The samples were grown in the temperature range of 220–300°C and consist of an epitaxial layer, 200–1000 Å thick, on the substrate material. The measurements reveal that, for small lattice mismatches (≲ 0.1%), the thicker epitaxial layers contain a high concentration of dislocations. Results on the thinner layers demonstrate the existence of strain as indicated by the ‘kink angle’ between {110} planes of the strained layer and substrate, but often with the sense of the angle for best channeling opposite to that expected from known lattice constants. The results are discussed in terms of Sn diffusion, the critical thickness for coherent growth, and channeling effects in strained layers.