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

The leakage current (I_L) annealing at elevated temperatures and the corresponding changes of the 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 the resistivities, three annealing stages have been observed: (1) the transformation of carbon related defects at 72°C; (2) slight decrease of the peak E_c-0.4 eV at 150°C, and (3) significant decrease of the peak E_c-0.4 eV at 350°C. The leakage current has been found to decrease monotonously in the temperature range of 20-150°C. A sharp decrease of I_L was observed at 350°C due to the annealing of the V-V center for heavily irradiated detectors, whereas I_L showed a slight saturation tendency for detectors irradiated to low neutron fluence. The V-V center has been found to be dominant in the formation of the E_c-0.4 eV peak and in the annealing of the leakage current. For low resistivity detectors, an anneal at 72°C was needed to stimulate the decrease of the effective impurity concentration (N_eff) of the detectors irradiated by high neutron fluence (1-2)×10¹⁴ n/cm². In addition, low resistivity detectors have been found to be tolerant in terms of N_eff stability to the 350°C anneal, favorable to the recovery of I_L after irradiation with high neutron fluence