Stationary and transient photocurrents in some amorphous Ge-As-Se thin films

The stationary and transient characteristics of photoconductivity in thermally deposited amorphous Ge0.07As0.07Se086 thin films, with the theoretically calculated mean coordination number Z=2.21, are reported. Introduction of the metallic elements (Sn and Ge) in selenide and sulphide (As2S3, As2Se3, As-S-Se) glasses, lead to the appearance of the tetrahedral structural units in the base glasses, which change the mean coordination number Z. These changes lead to non-monotonous changes of the electrical, optical and photoelectrical characteristics, depending on the glass composition. It was found that the dependence of the photocurrent on light intensity has a power-law behavior I-ph similar to F-beta(1.0 <=beta <= 0.5), which is characteristic for the amorphous semiconductors with the exponential distribution of the localized states in the band gap E-g.