Positron annihilation spectroscopy was used to identify Si and C vacancies as being irradiation-induced defects in 6H-SiC. The Si vacancies were shown to have ionization levels, at Ec–0.6eV and Ec–1.1eV below the conduction-band edge, by detecting changes in positron trapping under monochromatic illumination. These levels were attributed to (2–/1–) and (1–/0) ionizations of the isolated Si vacancy. In as-grown n-type 6H-SiC, a native defect complex which involved VSi was shown to have an ionization level which was slightly closer to the conduction band; at roughly Ec–0.3eV. These results were further used to give microscopic interpretations to the effects seen in optical-absorption spectra and to the electrical levels observed previously by means of deep-level transient spectroscopy.

Optical Transitions of the Silicon Vacancy in 6H-SiC Studied by Positron Annihilation Spectroscopy. S.Arpiainen, K.Saarinen, P.Hautojärvi, L.Henry, M.F.Barthe, C.Corbel: Physical Review B, 2002, 66[7], 075206 (10pp)