ZNS/ZNSE STRAINED-LAYER SUPERLATTICES UNDER PRESSURE

First-principles density-functional calculations of the electronic properties of ZnS/ZnSe (001) strained layer superlattices are used to investigate the influence of hydrostatic pressure on the valence-band offset (VBO). Three different strain mode's corresponding to various values of the relative thicknesses of the two types of layers are considered. The pressure coefficients of the VBO's are found to be very sensitive to the strain mode. A I --> II type conversion associated with the conduction-band crossover between the ZnSe well layers and ZnS barrier layers is found, in agreement with recent experimental data. The pressure behavior of the key quantities (VBO's, bulk moduli, energy gaps) is discussed for various strain modes.