Dependence of pseudomorphic semiconductor band gap on substrate orientation

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Abstract
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.