Electron paramagnetic resonance was used to study the TV2a center in 4H-SiC, which was previously attributed to the isolated Si vacancy but with different charge states: neutral, single negative, and triple negative, corresponding to different spin states S = 1, S = 3/2 and S = ½, respectively. The TV2a electron paramagnetic resonance spectra observed in dark and under light illumination in as-grown high-purity semi-insulating 4H-SiC in the absence of the negatively charged Si vacancy (VSi-) provide direct evidence confirming the spin triplet (S = 1) ground state of the center. A model with a triplet ground state and a singlet excited state was proposed to explain previously obtained results. The TV2a center could be detected in as-grown material annealed at 1600C.

Silicon Vacancy Related TV2a Center in 4H-SiC. N.T.Son, Z.Zolnai, E.Janzén: Physical Review B, 2003, 68[20], 205211 (5pp)