Influence of hydrogen on electronic transport in dc triode sputtered amorphous silicon

The electron drift mobility μn in dc triode sputtered amorphous hydrogenated silicon (a-Si:H) has been measured using a time of flight experiment. Moreover the product of the mobility by the lifetime (μn τn) has been determined from the steady state photoconductivity. Thus it has been possible to study the influence of hydrogen on both mobility and lifetime. The results indicate that the incorporation of hydrogen in a-Si:H greatly increases the electron lifetime but has little effect on the trap limited mobility. This behavior can be explained in the following way: the H incorporation reduces the number of deep lying localized states, corresponding to dangling bonds and acting as recombination centers, but has little influence on the states in the conduction band tail, which control the trap limited mobility.