Dispersive transport and electronic structure of amorphous silicon alloys

Recent experimental data on the dispersive transport and recombination lifetime in $a$-Si: H as functions of both phosphorus doping and temperature are analyzed using the results of a computer simulation. We conclude that undoped $a$-Si: H contains a distribution of deep charged intrinsic electron traps and a Gaussian band tail. The introduction of phosphorous leads to the formation of relatively shallow traps, which are also distributed in energy. The observed increase in recombination lifetime with phosphorus doping can be attributed entirely to the existence of these shallow traps, rather than to a change in the nature of the recombination centers.