Bias-dependent annealing of radiation damage in neutron-irradiated silicon p+-n-n+ diodes

Silicon pad diodes fabricated on n-type substrates were irradiated with fast neutrons from the TRIGA reactor facility to fluences around 5×1013 n/cm2. Annealing of radiation-induced defects was monitored via the full depletion voltage (FDV) obtained from C–V measurements, both during and after irradiation. As much as 50% difference in FDV was observed to appear between biased and unbiased diodes in a few hours after irradiation, with the biased diodes having the higher value. The FDV difference persists through later stages of annealing and reverse annealing. Upon switching off the bias voltage, the difference in FDV diminishes within days at room temperature. Observation of different effective dopant concentrations within the same detector in regions with and without electric field provides further evidence for bias-dependent annealing. No bias effect is seen on the reverse-current annealing.