Positron lifetime spectroscopy was used to detect vacancy-related defects in as-received and 12MeV proton-irradiated 6H-SiC crystals. It could be deduced, from the temperature dependence of the lifetime spectra decomposition, that neutral and negatively charged vacancy defects existed in crystals before and after proton irradiation at low fluence (less than 4 x 1015/cm2). Neutral vacancies were detected after irradiation to high fluences (greater than 4 x 1016/cm2). Negatively charged VSi silicon monovacancies with a 202ps lifetime were detected at low temperatures in as-received n-type 6H-SiC, and after irradiation to low fluences. Neutral VSi-C divacancies, associated with the 225ps lifetime, were produced by irradiation and dominated positron trapping at room temperature. In addition, various types of ionic acceptor were detected. One of them acted as a strong trapping center; even at room temperature.

Silicon Vacancy-Type Defects in As-Received and 12MeV Proton-Irradiated 6H-SiC Studied by Positron Annihilation Spectroscopy. L.Henry, M.F.Barthe, C.Corbel, P.Desgardin, G.Blondiaux, S.Arpiainen, L.Liszkay: Physical Review B, 2003, 67[11], 115210 (10pp)