Orientational Superlattices Formed by CuPt-Ordered Zinc-Blende Semiconductor Alloys

We performed a systematic study on a nonconventional semiconductor heterostructure - orientational superlattices (OSL's) - based on CuPt-ordered Zinc-blende alloys. Instead of the band offset in conventional superlattices, it is the discontinuity in the angular momentum which brings about the superlattice effects in orientational superlattices. Valence-band structures of five polytypes of OSL'sformed by CuPt-ordered GaInP2 layers have been classified according to their symmetries and calculated numerically by using the envelope-function approximation for structures with different periods, ratios of layer thickness, and degree of order. On one hand, features similar to those in conventional superlattices - wave-function modulation, band-gap modification, and the formation of subbandsand minigaps - can be achieved purely from an orientational alternation of the semiconductor layers. On the other hand, the dependence of energy levels on layer thickness and the wave-function distributions in OSL's are distinct from that in conventional superlattices.