Radiation effects on a GE:GA photoconductive detector

We have investigated radiation effects on a Ge:Ga photoconductive infrared detector at low photon background level of 4×10⁸ ph cm^‑2s^‑1, using Cobalt 60 as a gamma ray source. The irradiation immediately induced spike noises which degrded NEP (short term effect), while it gradually increased responsivity (long term effect). After the removal of the gamma ray source, the spikes disappeared while the responsivity still stayed in a higher level and gradually decreased with a time scale of several hours. The responsivity-change-rate before and after the irradiation is smaller for a higher bias voltage. Finally we have made the first trial to cure the long term effect, using a flashing procedure and have found out its effectiveness.