Silicon vacancy-type defects in as-received and 12-MeV proton-irradiated 6H-SiC studied by positron annihilation spectroscopy -: art. no. 115210

Positron lifetime spectroscopy is used to detect vacancy-related defects in as-received and 12-MeV proton-irradiated 6H-SiC crystals. We can infer from the temperature dependence of the lifetime spectra decomposition that neutral and negatively charged vacancy defects exist in crystals before and after proton irradiation at low fluence (less than or equal to4x10(15) H+ cm(-2)). Neutral vacancies are detected after irradiation at high fluence (greater than or equal to4x10(16) H+ cm(-2)). Negatively charged V-Si silicon monovacancies with 202+/-8 ps lifetime are detected at low temperature in as-received n-type 6H-SiC and after irradiation at low fluence. Neutral VSi-C divacancies associated with the (225+/-5)-ps lifetime are produced by irradiation and dominate the positron trapping at room temperature. In addition, different types of ionic acceptors are detected. One of them acts as a strong trapping center even at room temperature.