Positron annihilation investigation of electron irradiation-produced defects in 6H-SiC

Abstract

Electron irradiation of bulk n type 6H-SiC was done at 100 K and at 285 K. Irradiation at 100 K caused a new positron lifetime of 152 ps which persisted up to 450 K. Irradiation at 285 K caused a positron lifetime of 174 to 200 ps, depending on irradiation conditions, and it persisted up to 1500 K. These two lifetimes are ascribed to carbon vacancies (152 ps) and to neutral silicon vacancies (174–200 ps), which undergo a transformation to a carbon vacancy-carbon antisite pair near 1000 K. Introduction rates for the positron-detected vacancies significantly exceed reported rates for defects detected by electron paramagnetic resonance and deep level transient spectroscopy. In addition to creating vacancies, irradiation also caused an increase in the response from grown-in vacancy clusters, and this effect annealed out below 600 K. Based on this work, as well on works on Si and C (diamond) there is a simple empirical correlation between Doppler data and lifetime data.