Numerical simulation of 60Co-gamma irradiation effects on electrical characteristics of n-type FZ silicon X-ray detectors

This paper describes the gamma irradiation effects on the electrical characteristics of n-type float zone (FZ) silicon detectors by incorporating a 4-level 60Co-gamma radiation damage model in the commercial device simulator for plasma X-ray tomography diagnostics. In the simulations, a segmented n-type silicon detector (i.e. p+–n–n+ structure) is considered with varying substrate resistivity (ρ = 5.4, 2.5, and 0.3 kΩ cm). The simulation results have been validated with the reported experimental measurements carried out on similar device structures. The 60Co-gamma irradiation induced changes in the electrical characteristics of the detectors are analyzed up to the dose of 3500 Mrad. The possible gamma induced degradation in the X-ray response of the detectors is investigated from the changes in the effective doping concentration and the leakage current of the detectors. The survival of the gamma irradiated detectors is predicted from the simulation studies. The comparison between the 60Co-gamma and 14.1 MeV neutron irradiation effects (typical fusion environments) on silicon detectors is attempted.