Bias-dependent radiation damage in high-resistivity silicon diodes irradiated with heavy charged particles

High-resistivity p/sup +/-n-n/sup +/ planar diodes were irradiated with neutrons to fluences up to 2*10/sup 14/ cm/sup -2/ 1 MeV neutron NIEL equivalent and with pions to 0.47*10/sup 14/ cm/sup -2/. Special care was taken to irradiate samples under strictly controlled conditions (temperature, bias). The influence of detector biasing on the effective dopant concentration as measured with the C-V method was studied. Permanently biased diodes exhibit about two times higher [N/sub eff/] after beneficial annealing has been completed. After switching off the bias the difference between biased and unbiased samples diminishes with a temperature-dependent annealing time. Part of the difference is attributed to a bistable defect since it recovers if the bias is re-applied for a few days at room temperature. The bias-induced damage was estimated to result in a 40-70 V addition to required bias for detectors in the ATLAS SCT after 10 years of LHC operation. (18 refs).