Optical properties of the amorphous semiconductor (GeS2)(1-x)(Bi2S3)(x) system under high pressure

We measured the change of the absorption spectra under high pressure to stu dy the optical properties of the amorphous (GeS2)(1-x)(Bi2S3)(x) system, an d we also studied the change of local atomic structures under pressure with increasing Bi2S3 concentration. The optical edge exhibits a red shift with increasing pressure, and depends strongly on the Bi2S3 concentration. Espe cially for the concentration range x = 0 to 0.05, the optical gap E-o decre ases non-linearly in the pressure range 2.0 to 4.0 GPa, and large hysteresi s effects are observed in the GeS2-rich composition. For the concentration range 0.1 less than or equal to x, the optical gap E-o decreases linearly w ith pressure, and no hysteresis effects are observed. As the existence of i nternal void structure is considered to be the origin of the hysteresis, it is considered that the irreversible destruction of the void structure indu ces the nonlinear decrease of the optical gap E-o.