Heteroepitaxy of CuInxSey: a review of the material and interface properties

Molecular beam epitaxy has been used to grow heteroepitaxial CuInxSey layer s on Si and GaAs substrates. Layers of different Cu/In ratios have been gro wn to study the formation of different phases such as CuInSe2 chalcopyrite (alpha-phase) and defect-chalcopyrite/stannite phases (beta-phase) in this material system. A variety of characterization methods are used to identify if the layer is a single phase compound or a mixture of two compounds. Str uctural and optoelectronic properties strongly depend on the Cu/In ratio. E pitaxial layers with an ion channeling yield of 7% and an X-ray rocking cur ve width of about 770 arcsec have been grown. Linear and planar defects as well as interdiffusion of elements are expected in the interfacial region d ue to layer-substrate mismatch and growth conditions. These defects have be en identified with high resolution transmission electron microscopy. The ch emical composition of the interfacial layer has been investigated by Ruther ford backscattering spectroscopy, microprobe energy dispersive X-ray analys is and X-ray diffraction. An interfacial CuSexSiy layer is formed during th e growth of CuInxSey on Si. In the case of GaAs substrates, Ga from the sub strate diffuses into the CuInxSey and a quaternary compound Cu(In,Ga)(x)Se- y is formed at the interface. (C) 2000 Elsevier Science S.A. All rights res erved.