Proton-implantation-induced defects in n-type 6H- and 4H-SiC: An electron paramagnetic resonance study

The microscopic structure and introduction rate of point defects in n-type 6H- and 4H-SiC generated by room-temperature proton implantation have been studied by the electron paramagnetic resonance technique. In order to selec tively study the effects of defect introduction in the trace region, 12-MeV implantation in 300-mum-thick samples was employed, for which the protons completely cross the sample. In both polytypes we observe three dominant pa ramagnetic defects attributed to the Si monovacancy in the negative charge state and the neutral Si monovacancy in the hexagonal and quasicubic lattic e sites, respectively. The concentration of all three defects increases lin early with proton dose. Their total introduction rate is similar to 19 cm(- 1). which amounts only to 4% of the concentration expected from SRIM simula tions. No carbon-vacancy-related defect is observed. Thermal annealing at 1 100 degreesC is sufficient to anneal out the V-Si defects and to restore n- type conductivity. The observation of the neutral Si vacancy at hexagonal a nd quasicubic sites under thermal equilibrium conditions at 4 K does not su pport their previous assignment to an excited state.