Positron lifetime spectroscopic studies of as-grown 6H-silicon carbide

Positron lifetime spectroscopy has been employed to study the as-grown n-type 1.2 x 10(18) cm(-3) N-doped and p-type 1.8 x 10(18) cm(-3) Al-doped 6H-silicon carbide in the temperature range 10K-300K. For the p-type material, a positron trapping site, which has a lifetime of 225 +/- 11 ps, was found and is attributed to positron annihilating from the V(Si)V(C) divacancy-related defect having a neutral charge. For the case of the n-type material, a positron trapping centre having a lifetime of 200 +/- 9 ps, attributed to a V(Si)-related defect, and a shallow trap were observed. The shallow trap, having binding energy of 18 meV was attributed to Rydberg-like states resulting from positron binding with a negative ion.