Recombination at correlated dangling bonds and the effects of Fermi level position on steady-state photoconductwiry in amorphous silicon

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Abstract
A simple recombination model is proposed in order to explain effects of Fermi level position on steady-state photoconductivity in a-Si: H. The model assumes positively correlated dangling bonds as the only localized states in the gap and takes into account the occupation statistics of correlated defect centres in the dark and under illumination. The steady-state photoconductivity and its dependence on light intensity are investigated as a function of the Fermi level position in the gap. Effects of changes in the correlation energy and in the ratio of the cross-sections of charged and neutral recombination centres are also studied, as well as the dependence of the photoconductivity on the total density of defects. The results show good agreement with experimental data for undoped, and for phosphorus- and boron-doped a-Si:H.