Pressure Dependence of Energy Band Gap and Photoluminescence in Ag-x Cu1-xGaS2 Single Crystals

Abstract

Pressure dependence of energy band gaps and photoluminescence spectra in single crystals of AgxCu1xGaS2 grown by the horizontal Bridgman and the iodine transport methods were investigated for the first time. The pressure coefficient of the band gap showed a quadratic increase with the Ag composition. Such quadratic variation is in contrast with that in CuInxGa1-xSe2 single crystals. This phenomenon means that the bulk modulus and the volume deformation potential depend on the composition x. From the pressure coefficients of the photoluminescence (PL), the donor acceptor transition from the shallow donor to the deep acceptor show the same tendency as the pressure dependence of the energy band gaps with composition x. We suggest that the p-d hybridization in the valence band increases nonlinearly with the Cu composition.