Pulsed slow-positron beam-based positron lifetime spectroscopy was used to investigate the nature of acceptors and the charge states of vacancy-type defects in low-energy proton-implanted 6H-type material. It was deduced, from the temperature dependence of the lifetime spectra, that neutral and negatively charged vacancy clusters existed within the track region. Depending upon the annealing conditions, they could give rise to positron lifetimes of 257, 281 and 345ps. The 281ps cluster was suggested to have an ionization level near to the middle of the band-gap. By means of a comparison with theory, the 257 and 280ps lifetimes were attributed to (VC–VSi)2 and (VC–VSi)3 clusters, respectively. In addition, other acceptors of ionic type acted as strong trapping centers at temperatures below 150K. Neutral monovacancy-like complexes, with a lifetime of 160ps, were also detected after 900C annealing.

Evidence for Negatively Charged Vacancy Defects in 6H-SiC after Low-Energy Proton Implantation. D.T.Britton, M.F.Barthe, C.Corbel, A.Hempel, L.Henry, P.Desgardin, W.Bauer-Kugelmann, G.Kögel, P.Sperr, W.Triftshäuser: Applied Physics Letters, 2001, 78[9], 1234-6