Electron irradiation of bulk n type 6H-SiC was performed at 100K and at 285K. Irradiation at 100K caused a new positron lifetime of 152ps which persisted up to 450K. Irradiation at 285K caused a positron lifetime of 174 to 200ps, depending upon the irradiation conditions, and it persisted up to 1500K. These 2 lifetimes were attributed to C vacancies (152ps) and to neutral Si vacancies (174–200ps), which underwent transformation to a C-vacancy plus C-antisite pair near to 1000K. The introduction rates of the positron-detected vacancies significantly exceeded the 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. This effect annealed out below 600K. On the basis of this work, as well as work on Si and C (diamond), it was concluded that there was a simple empirical correlation between Doppler data and lifetime data.

Positron Annihilation Investigation of Electron Irradiation-Produced Defects in 6H-SiC. S.Dannefaer, D.Kerr: Diamond and Related Materials, 2003, 13[1], 157-65