Prediction and measurement of the optical properties of amorphous GexSe1-x

The optical properties of amorphous thin films of GexSe1-x, with 0.2 < x < 1.0, prepared by RF sputtering, have been measured and the optical band gaps, E-g, and the long-wavelength refractive indexes, n(0), determined as a function of composition. The local atomic structure of the films has been determined using EXAFS. This structural data has then been used to predict the optical properties. Comparison of the predictions with the experimental data shows very good agreement between the two, including the existence of a maximum in the band gap at the stoichiometric composition. We believe that the optical properties of any semiconducting amorphous alloy may be predicted using the theory described here. (C) 1998 Elsevier Science B.V. All rights reserved.