The microstructure of (112)-oriented CuInSe2 hetero-epitaxial layers, which had been grown using molecular beam epitaxy onto (111)-oriented Si wafers, was investigated by means of transmission electron microscopy. The experimental and calculated diffraction patterns of various zone axes were compared. It was noted that extra spots were caused by rotational twins on (112) growth planes. Six twin variants, rotated by 120, 60 or 180 about the [221] axis, were identified in the layers. It was suggested that the tetragonal chalcopyrite structure of the selenide, the crystal symmetry of the substrate, and variations in the growth conditions during growth were responsible for the formation of these twins. Coherent twin boundaries, as well as partially coherent boundaries of twin variants which were rotated by 60 and 180, were observed by using high-resolution transmission electron microscopy. The boundaries could be formed by inserting partial dislocations, with a Burgers vector of a/6<11¯1>, into the selenide structure. It was concluded that annealing of the samples led to the annihilation of these partial dislocations, and thereby reduced the density of twins in the layers.

M.Krejci, A.N.Tiwari, H.Zogg, P.Schwander, H.Heinrich, G.Kostorz: Journal of Applied Physics, 1997, 81[9], 6100-6