Steady-state photoconductivity in amorphous arsenic selenide compounds

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Abstract
The steady-state photoconductivity has been measured and analysed for vitreous a-As2Se3 and evaporated a-As2Se3 films, and for non-stoichiometric vitreous As-Se alloys. Special attention was paid to the dependence on illumination energy and intensity, and to the temperature dependence of the photocurrent. The spectral distribution of the photo-current provides evidence for a defect level about 1.4 to 1.5 eV into the gap for all bulk samples, irrespective of composition. The temperature dependence can at the same time, and again for bulk samples, be comprehensively analysed in terms of a two-defect-level energy diagrams, which is compatible with the optical 1.4 eV level. For evaporated layers, on the other hand, no spectroscopic feature could be resolved, nor could a self-consistent result be obtained for the temperature dependence analysis in terms of discrete gap levels.