ANNEALING PROCESSES OF VACANCY-TYPE DEFECTS IN ELECTRON-IRRADIATED AND AS-GROWN 6H-SIC STUDIED BY POSITRON LIFETIME SPECTROSCOPY

Annealing processes of vacancy-type defects in 3 MeV electron-irradiat ed and as-grown 6H-SiC have been studied by positron lifetime spectros copy. Vacancy-type defects giving rise to a positron lifetime of 183 p s were detected in as-grown n-type specimens. They were found to be an nealed at around 1400 degrees C and were related to silicon vacancies, possibly complexes of silicon vacancies and nitrogen atoms. Defects r elated to carbon vacancies, silicon vacancies, and divacancies were fo und to be created by electron irradiation. The defects related to carb on vacancies and divacancies were found to be annealed up to 500 degre es C. The defects related to silicon vacancies were found to be anneal ed at around 750 and 1400 degrees C. The former annealing stage was in ferred to be due to migration of silicon vacancies to internal sinks o r nitrogen atoms to form complexes of silicon vacancies and nitrogen a toms. The latter annealing stage was explained as due to annihilations of the complexes as well as the case of as-grown specimens. (C) 1996 American Institute of Physics.