Positron annihilation of vacancy-type defects in neutron-irradiated 4H–SiC

Annealing behavior of vacancy-type defects in n-type 4H–SiC, which was irradiated with neutrons up to a dose of 3.2 × 1021 m−2 (E > 1 MeV) at 20 °C, was investigated by positron annihilation spectroscopy. Isochronal annealing results indicate that there are four different recovery stages in the irradiated 4H–SiC. In stage I, in the temperature range of 20–100 °C, the defect recovery is attributed to recombination between close vacancies and interstitials, and carbon and silicon clusters are formed by the migration of their interstitials. In stage II (200–1100 °C), carbon and silicon interstitials disappear at permanent sinks due to the long-range migration. Silicon and carbon vacancies move actively in stage III (1200–1400 °C). In stage IV (>1400 °C), more stable silicon vacancy complexes dissociate. Although, no vacancy-type defects are observed in 4H–SiC after annealing at 1600 °C, interstitial-type or anti-site defects are stable.