Electric properties of undoped hydrogenated amorphous silicon semiconductors irradiated with self-ions

This paper reports dark conductivity (DC), photoconductivity (PC), and Seebeck coefficient variations of undoped hydrogenated amorphous silicon semiconductors irradiated with protons and Si ions. Both the DC and PC values show nonmonotonic variations with increasing a fluence in the case of proton irradiation, whereas the monotonic decreases are observed in the case of Si ion irradiation. From results of the Seebeck coefficient variation due to proton irradiation, it is shown that the increase in DC and PC in the low fluence regime is caused by donor-center generation. Also, it is shown by analyzing the proton energy dependence and the energy deposition process that the donor-center generation is based on the electronic excitation effect. On the other hand, the decrease in DC and PC in the high fluence regime is attributed to the carrier removal effect and the carrier lifetime decrease due to the accumulation of dangling bonds, respectively. The dangling bond generation due to ion irradiation is mainly caused by the displacement damage effect and therefore it is different from the generation process in the Staebler–Wronski effect.