Carbon and silicon vacancies in electron-irradiated 6H-SiC

Positron-lifetime and Doppler-broadening spectroscopies were used to investigate vacancies formed by 2.2- and 10-MeV electrons. Carbon vacancies yield a positron lifetime of 160 ps, only 15 ps longer than the bulk lifetime, and the Doppler-broadening S parameter is very close to that for the bulk. For silicon vacancies the positron lifetime is 260 ps and the S parameter is 1.12 times the bulk value. In n-type materials the defects are neutral, whereas in p-type materials no vacancies are detected. Introduction rates of carbon and silicon vacancies were also determined.