DEPENDENCE OF PSEUDOMORPHIC SEMICONDUCTOR BAND-GAP ON SUBSTRATE ORIENTATION

For a given misfit we examine the band-gap variation of a pseudomorphic overlayer on a thick substrate as a function of substrate orientation. The strain tensor is found to be a strong function of the substrate orientation. For both direct and indirect band-gap overlayers, this results in a significant variation in the band gap as the substrate orientation is changed. However, for indirect band-gap layers, such as SiGe alloys grown on Si substrates, the change in band gap is accompanied by a lifting of conduction-band-edge degeneracies. The magnitude of this splitting may be as large or larger than the change in the band gap.