Determination of energy of defect centres in a-Se78Ge22 thin films

Abstract

Steady-state photoconductivity measurements have been performed on a-Se78Ge22 thin films prepared by vacuum evaporation. The temperature dependence of the photocurrent shows a maximum at a high temperature. A clear transition from monomolecular to bimolecular recombination is also observed at the same temperature. The observed behaviour is explained by assuming two sets of defects of different capture cross-sections, and different time constants. The energy location of these sets of defects is determined from the experimental data. A superlinear dependence of photocurrent on intensity is observed in the films, which is explained in terms of the energy distribution of two discrete localized states with different cross-sections.