Band offsets and uniaxial stress effects in CdZnS/ZnS straindlayer superlattices

Abstract

Strain induced band offsets of the conduction band and valence subbands in Cd_xZn_lxS/ZnS superlattices have theoretically been calculated on the basis of the modelsolid theory taking into account of spinorbit energy(Δ_so). The conduction and valence band offsets have been estimated as a function of the well layer thickness and Cd composition (x), and as a result the valence band offsets which are derived from heavy hole and light hole bands increase with both decreasing the well layer thickness and Zn composition. Effect of external uniaxial compressive stress (ε) on the band offsets indicates that the energy difference between the heavy hole band in CdZnS well and the light hole band in ZnS barrier increases monotonously with applied stress. On the other hand, that of light hole bands shows a quadratic energy shift as a function of uniaxial stress and has a minimum energy value around ε/Δ_so. It is pointed out that a large energy difference in uniaxial deformation potential constants between CdS and ZnS shows a unique behaviour which significantly modifies the electronic states in the CdZnS based quantum well structures under uniaxial stress.