Vacancies and deep levels in electron-irradiated 6H SiC epilayers studied by positron annihilation and deep level transient spectroscopy

Abstract

The annealing behavior of defects in n-type 6H SiC epilayers irradiated with 2 MeV electrons have been studied using positron annihilation and deep level transient spectroscopy. Vacancy-type defects are annealed at 500–700 °C and 1200–1400 °C. From the analysis of Doppler broadening spectra (core electron momentum distribution), the latter annealing process is attributed to the disappearance of complexes related to silicon vacancies and not to nearest neighbor divacancies. Among the observed deep levels, the $E_1{\mathrm{/E}}_2$ levels show similar annealing behavior to that of positron annihilation centers above 1000 °C. It is thus proposed that the $E_1{\mathrm{/E}}_2$ levels originate from complexes containing silicon vacancies.