The annealing out of vacancy-type defects from 3MeV electron-irradiated or as-grown 6H-type samples was studied by means of positron lifetime spectroscopy. It was found that vacancy-type defects which gave rise to a positron lifetime of 183ps were present in as-grown n-type specimens. They were found to be annealed out at about 1400C, and were related to Si vacancies; possibly in the form of complexes of Si vacancies with N atoms. Defects which were related to C vacancies, Si vacancies and di-vacancies were found to be created by electron irradiation. The defects which were associated with C vacancies and di-vacancies were found to anneal out below 500C. The defects which were associated with Si vacancies annealed out at about 750 and 1400C. The former annealing stage was suggested to be due to the migration of Si vacancies to internal sinks, or of N atoms to form complexes of Si vacancies and N atoms. The later annealing stage was suggested to be due to the annihilation of the complexes.

A.Kawasuso, H.Itoh, S.Okada, H.Okumura: Journal of Applied Physics, 1996, 80[10], 5639-45