Composition dependence of the hydrostatic pressure coefficients of the bandgap of ZnSe1-xTex alloys

Optical absorption experiments were performed using diamond-anvil cells to measure the hydrostatic pressure dependence of the fundamental bandgap of ZnSe_1-xTe_x alloys over the entire composition range. The first- and second-order pressure coefficients were obtained as a function of composition. The coefficients do not vary linearly between the ZnSe and ZnTe end-point values. Starting from the ZnSe side, the magnitude of both coefficients increases slowly until x≈0.7, which is the point where the ambient-pressure bandgap shows a minimum. At larger values of x the coefficients rapidly approach the values of ZnTe. The large deviations of the pressure coefficients from the linear interpolation between ZnSe and ZnTe are explained in terms of the band anticrossing model.