Design of Pseudo-Quaternary Alloy of ZnCdSSe by Superlattices Lattice-matched to GaAs

Abstract

In this paper, we propose two superlattice structures as pseudo-quaternary ZnCdSSe layers. They consist of three layers or four layers in a cycle with three kinds of binary compound materials, i.e., ZnS, ZnSe and CdS. In order to estimate the equilibrium in-plane lattice constant of these layers, a general expression for superlattices consisting of n (n=2, 3, 4, …) layers in a cycle has been derived by minimizing the total elastic strain energy. The effective bandgap for the superlattices with different combinations of the layer thickness in a cycle were calculated using Kronig-Penney model, where the strain effect was taken into account in calculating the bandgap and the band offset. The calculated results of the effective bandgaps were compared with the bandgap of ZnCdSSe quaternary alloy.