Reversible changes in temperature dependence of electric conductivity of hydrogenated amorphous silicon caused by proton irradiation

Sato, Shinichiro; Oshima, Takeshi

We investigate temperature dependence of electric conductivity and photoconductivity of hydrogenated amorphous silicon (a-Si:H) thin films due to energetic proton irradiation and clarify the change in dominant electric conduction mechanism. The results show that the high fluence proton irradiation changes the dominant electric conduction mechanism from the band transport of thermally excited carriers through the extended states to the hopping transport based on the carrier transport via localized states near the Fermi level. The hopping conduction has the weak temperature dependence which disappears at elevated temperature and the strong temperature dependence based on the band conduction appears again. We conclude that the change in dominant electric conduction mechanism is caused by the increase in localized density of states.