Evolution of the native defects in unintentionally doped 4H-SiC during annealing process

With isothermal annealing treatment at 1873 K, unintentionally doped 4H-SiC epitaxial layers grown by low-pressure chemical vapor deposition (LPCVD) have been studied using electron spin resonance (ESR) and low temperature photoluminescence (PL). ESR and PL spectra show that the native defects are the mixture of carbon vacancy (V_C) and its extended point defects. The decrease of key parameter g vector is obtained from ESR spectra with annealing time prolonged. Meanwhile the full width at half maximum (FWHM) becomes wider and the peak shifts from green to yellow luminescence in PL spectra. This phenomenon results from strong interaction among the intrinsic defects during the isothermal annealing process. The interaction of native defects affects the way of native defect combination and then makes the energy level of native defects varied with annealing time changed from 10 min to 60 min.