Elevated temperature annealing of the neutron induced reverse current and corresponding defect levels in low and high resistivity silicon detectors

A new aspect of degradation phenomena of neutron irradiated silicon detectors has been revealed which consists in the significant influence of carbon related defect transformation on the detector reverse current (I_rev). The annealing of the reverse current at elevated temperatures and the corresponding changes of the deep level transient spectroscopy (DLTS) spectra of defects for fast neutron irradiated silicon detectors, fabricated on high (4-6) kΩ-cm, moderate (0.5-1.0 kΩ-cm) and low (<100 Ω-cm) resistivity silicon material have been investigated. For all resistivity silicon detectors studied in this work, three annealing stages of the defects with deep levels in the energy band gap have been observed: 1) the transformation of carbon related defects in the temperature range of 20-72°C; 2) decrease of the peak E_c-0.4 eV at 150°C, and 3) complete annealing of the peak E_c-0.4 eV at 350°C. The transformation of carbon related defects consisted in the annealing of interstitial carbon (C_i) and simultaneous generation of C _i-O_i complex and was accompanied by a significant reduction of the reverse current. The decrease of the peak E_c-0.4 eV was observed in the temperature range of 72-350°C and was affected by both the annealing of the E-center (V-P complex) and single minus charge state of divacancy (VV^-) and by the changes in the filling of the deep levels in high or moderate resistivity Si. The results show the comparable role of the V-P complex and VV^- center in formation of E_c-0.4 eV defect in high and moderate resistivity silicon