Thermally stimulated currents analysis of the shallow levels in irradiated silicon detectors

Thermally stimulated current measurements in the temperature range 10-20 K have been performed on a set of silicon p(+)/n/n(+) junction detectors. The samples were irradiated with fluences from 6.4 x 10(11) cm(-2) up to 1.1 x 10(14) cm(-2) (1 MeV neutron equivalent) in order to investigate the changes in the shallow level concentrations induced by irradiation. The measurements showed a broadening of the peak shape and a decrease in the height of the spectral components as the fluence increases. A phosphorus removal of approximately one order of magnitude is observed for the most irradiated sample, while the boron component is almost independent of the fluence. At the highest level of irradiation the phosphorus and boron levels show comparable concentrations.