ALLOY EFFECTS ON THE BAND OFFSETS OF ZNSXSE1-X-ZNSE HETEROSTRUCTURES

The band offsets of ZnSxSe1-x-ZnSe heterostructures are calculated within a self-consistent sp3s* tight-binding model including spin-orbit coupling considering several sulfur concentrations x and in the two extreme strain states that can be imposed on the structure (strained to a ZnSe or to a ZnSxSe1-x lattice parameter). The commutativity of the valence- and conduction-band offsets is examined. The conduction-band offset DELTAE(c) is found to be weak for x congruent-to 1 and whatever the strain state imposed. The variation of DELTAE(c) with respect to the sulfur concentration x is mainly driven by the bowing effect of the band gap. We show that the vanishing value of the conduction-band offset can be obtained through a diminution of the band-gap bowing effect which may be achieved in ZnSxSe1-x-ZnS1-xSex superlattices, leading to the possibility for these structures to be effective-mass superlattices.