Photo- and dark conductivity variations of solar cell quality a-Si:H thin films irradiated with protons

We investigated conductivity variations of hydrogenated amorphous silicon thin films during 10 MeV proton irradiations at fluences of 2.0×10¹³ or 4.0×10¹⁴ /cm² and for certain duration after stopping the irradiations. During the irradiation the conductivity initially increases and after the certain period of irradiation, it decreases. We also investigated behaviors of light-induced degradations before and after the irradiations. The light-induced degradation results indicate that the radiation-induced changes in the electrical properties do not completely return to their initial values after thermal annealing. Furthermore, our study indicates that the conventional mechanism governing electrical conduction of semiconductor materials under proton irradiation could be applied to high fluence regime. On the other hand, this model could not be extended to lower fluence regime, and thus another conduction mechanism does exist.