The influence of neutron irradiation upon defects and oxygen precipitation in Czochralski silicon were investigated. The vacancy-oxygen complex (VO, A-center) was one of the main defects formed in neutron-irradiated Czochralski silicon (CZ-Si). In this defect, the oxygen atom shares a vacancy, it was bonded to two silicon neighbours. Annealing of the A-center in varied neutron-irradiated CZ-Si consists of two processes. The first was trapping of VO by interstitial oxygen (Oi) in low-dose neutron-irradiated CZ-Si and the second was capturing of the wandering vacancy by VO, etc, in high-dose neutron-irradiated CZ-Si. With the increase of the irradiation dose, the annealing behaviour of the A-center was changed and the formation of the VO2 was depressed. It was found that V2 and V4 abound in high-dose irradiated CZ-Si. With the increase of the annealing temperature the monovacancy type defect was annihilated. The results showed that the formation of V4 was enhanced upon annealing at 400 to 600C and with the FTIR absorption peak at the wave number of 829/cm (VO) disappearing, 5 absorption peaks appeared. It could be concluded that these defect-impurity complexes prolong the lifetime of positrons. It was found that the high-dose irradiated greatly accelerated the oxygen precipitation which leads to a sharp decrease of the interstitial oxygen with the increase of the annealing time. At room temperature, the 1107/cm infra-red absorption band of interstitial oxygen became weak and broadens to low energy side. The bulk micro-defects, including stacking faults, dislocations and dislocation loops, were observed by optical microscopy. New or large stacking faults grew up when the silicon self-interstitial atoms were created and aggregate with oxygen precipitation.

Neutron Irradiation Defects in Czochralski Silicon. G.Chen, Y.Li, C.Liu: Physica Status Solidi C, 2009, 6[3], 669-76