ELECTRONIC-STRUCTURES OF HETERO-CRYSTALLINE SEMICONDUCTOR SUPERLATTICES

Crystal structures of hetero-crystalline superlattices made of materials with different crystalline structures are proposed and band structures of (hexagonal-diamond Si)/(cubic-diamond Si) and (wurzite ZnS)/(zinc-blend ZnS) superlattices are calculated using the first-principles pseudopotential method within the local-density approximation. It is shown that Si superlattices have indirect band gaps of energy around 1.1 eV, while ZnS superlattices have direct band gaps of energy around 3.8 eV. In both superlattices, the states around the fundamental gap show charge densities localized in one constituent layers, indicating that these superlattices give quantum well systems of good quality. Band offsets are also evaluated.