On the energy spectrum of vitreous arsenic sulphide

Abstract A brief review of an experimental study of reflectivity, absorption and photoconductivity spectra, and current-voltage characteristics of vitreous arsenic sulphide is presented. The absorption spectra were obtained in the high absorption range up to K = 10 5 cm −1 . The value of the forbidden band E g of vitreous As 2 S 3 obtained from the optical data is 2.4 eV. It is shown that the absorption edge at energies E E g has an exponential character due to localized states near the allowed band edges. Under the action of an electric field the exponential absorption edge shifts to a lower energy range obeying Franz' theory. From a study of the photoconductivity spectra and current-voltage characteristics in the nonlinear range some conclusions can be made concerning the energy distribution of the localized states in the forbidden band of the amorphous arsenic sulphide films.