Doping effects on post-hydrogenated chemical-vapour-deposited amorphous silicon

Abstract Conductivity and E.P.R. experiments are reported for boron- and phosphorus-doped chemical-vapour-deposited amorphous silicon film. In as-deposited films a large increase in the conductivity above a threshold dopant concentration is observed in both types of doped sample. Three resonances with g factors at respectively 2.0058, 2.0043 and 2.013 are observed. These results are interpreted by a simple model of electronic filling and emptying of the dangling bonds and tail states by the carriers supplied by the doping atoms. The effect on these properties of ‘adjustable’ hydrogen incorporation is analysed. For phosphorus doping, and for low hydrogenation in boron doping, the passivation of defects depends on the quantity of hydrogen, which explains the experimental results. The most striking result is the decrease in doping efficiency for strong hydrogenation observed in boron-doped films.