Leakage current of hadron irradiated silicon detectors - material dependence

The leakage current increase of silicon detectors irradiated with fast neutrons was measured in the fluence range from 10 to 10 cm for a wide range of different starting material. The oxygen concentration in the investigated silicon varied from 9×10 cm to below 2×10 cm and the carbon concentration from 2×10 cm to below 5×10 cm. Furthermore the resistivity differed from 100 Ωcm to 20 KΩcm for the used n-type and from 400 Ωcm to 2 KΩcm for the p-type silicon. It is found that up to the highest fluence the current related damage parameter alpha is almost independent of the initial resistivity and impurity concentration. After irradiation a universal annealing behavior for all material is observed which unmistakably indicates that the microscopic defects underlying the generation of leakage current are of intrinsic origin. Furthermore it is shown that the parameterization of the annealing behavior at an elevated temperature (here 60°C) provides an excellent tool for comparing the so-called hardness factors of different irradiation sources. As an example the hardness factors for the 24 GeV/c CERN Proton Synchrotron and the TRIGA research reactor in Ljubljana were determined to be 0.51 and 0.76 respectively.