MICROSCOPIC ANALYSIS OF DEFECTS IN A HIGH-RESISTIVITY SILICON DETECTOR IRRADIATED TO 1.7X10(15)N CM(2)/

Current-based microscopic defect analysis methods with optical filling techniques, namely current deep level transient spectroscopy (I-DLTS) and thermally stimulated current (TSC), have been used to study defec t levels in a high resistivity silicon detector (p(+)-n-n(+)) induced by very high fluence neutron (VHFN) irradiation (1.7x10(15) n/cm(2)). As many as fourteen deep levels have been detected by I-DLTS. Arrheniu s plots of the I-DLTS data have shown defects with energy levels rangi ng from 0.03 eV to 0.5 eV in the energy band gap. Defect concentration s of relatively shallow levels (E(t) < 0.33 eV) are in the order of 10 (13)cm(-3), while those for relatively deep levels (E(t) > 0.33 eV) ar e in the order of 10(14) cm(-3). TSC data have shown similar defect sp ectra. A full depletion voltage of about 27,000 volts has been estimat ed by C-V measurements for the as-irradiated detector, which correspon ds to an effective space charge density (N-eff) in the order of 2x10(1 4) cm(-3). Both detector leakage current and full depletion voltage ha ve been observed to increase with elevated temperature annealing (ETA) . The increase of the full depletion voltage corresponds to the increa se of some deep levels, especially the 0.39 eV level. Results of posit ron annihilation spectroscopy have shown a decrease of total concentra tion of vacancy related defects including vacancy clusters with ETA, s uggesting the breaking up of vacancy clusters as possible source of va cancies for the formation of single defects during the reverse anneal.