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

High-resistivity p(+)-n-n(+) planar diodes were irradiated with neutrons to fluences up to 9 x 10(14) cm(-2) 1 MeV neutron NIEL equivalent and with pions to 0.47 x 10(14) cm(-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-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. (C) 2000 Elsevier Science B.V. All rights reserved.