Photoconductivity and recombination in amorphous silicon alloys

Abstract

We have developed a new model to describe realistically the steady-state photoconductivity in amorphous silicon alloys. In agreement with experimental data, we find photoconductivity to be very dependent on the position of the dark Fermi level. This sensitization is a consequence of both a change in the recombination path together with the effects of dopant-created gap states. We also demonstrate the relationship between the power dependence of the photoconductivity and the dark-Fermi-level position and show that, as a result of space-charge neutrality, this dependence can be related to a characteristic energy slope of the density of states only in the absence of injected charge or dopants. Moreover, in agreement with recent experimental data, we find a power dependence of less than 0.5 for high-intensity illumination on $n$-type amorphous silicon.