Temporal electric conductivity variations of hydrogenated amorphous silicon due to high energy protons

Sato, Shinichiro; Sai, Hitoshi*; Oshima, Takeshi; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Kondo, Michio*

Electrical conductivity variations of undoped, n-type and p-type hydrogenated amorphous silicon (a-Si:H) thin films irradiated with various energy protons are systematically investigated in this study. Dark conductivity (DC) and photoconductivity (PC) of the undoped samples increased at first due to proton irradiation and then decrease dramatically with increasing proton fluence. However, increased PC was metastable and gradually decreased with time. Similar results were observed in the n-type a-Si:H, whereas the monotonic decrease was observed in the p-type one. The degrees of the DC and the PC decreases became lower as the irradiated proton energy was higher. The increases of both DC and PC are attributed to the temporal donor like center generation, although the additional proton irradiation decrease both the DC and PC by the accumulation of radiation-induced defects, which are act as deep traps and compensate carriers.