Studies of Annealing of Point Defects and Their Influence on the Electrical Degradation and Recovery Behaviors of Heavily Neutron Irradiated Silicon

We have investigated the annealing behaviors of point defects and their influence on the electrical degradation and recovery of heavily neutron irradiated silicon. It is found that high concentrations of divacancy (V-2) and vacancy-oxygen (VO) complexes are introduced in heavily irradiated silicon, which is responsible for the enhanced carrier recombination and therefore the observed drastic decrease of carrier lifetime. While the dopants deactivation from vacancy-phosphorus (VP) complexes and carrier compensation from VO and V-2 complexes result in the remarkable increase of resistivity. After post-irradiation isochronal annealing at 200-400 degrees C the carrier lifetime and resistivity exhibit insignificant changes, which is attributed to the transformation of V-2 and VO complexes into [VO+O-i], V2O, V3O complexes at 200-300 degrees C and the possible formation of VP-O complexes at 400 degrees C. While the heat treatments at elevated temperatures (>400 degrees C) result in the elimination of the majority of electrically active VmOn and the possible VP-O complexes, and therefore the carrier lifetime and resistivity of silicon begin to recover at 500 degrees C and 650 degrees C, respectively. However, the recovery of carrier lifetime is incomplete, which is due to the enhanced carrier-recombination from the survival defects with deep levels at E-C - 0.24eV and E-C - 0.44eV during annealing.