Effects of previous illumination on the conductity of an undoped film on amorphous, hydrogenated silicon

Observations have been made on the conductivity changes in a-Si:H films and in the activation energy after preliminary illumination, and also on the suppression of the temperature-dependent quenching of the band-band photoconductivity and superlinearity in the lux-ampere characteristics; explanations are given via the formation of an additional concentration of broken silicon bonds, which acquire a donor or acceptor character and correspondingly displace the Fermi level $E_F$ upwards or downwards in accordance with the equilibrium position of that level in the film. The recombination model is discussed.