Photo-induced electron paramagnetic resonance studies of nominally semi-insulating high-purity 4H-SiC revealed charge transfer from an intrinsic defect to the shallow B acceptor and N donor. At 4K, an incident photon energy of between 1.0 and 1.7eV produced an increase in paramagnetic B of approximately the same magnitude as the decrease in paramagnetic defect concentration. Below 80K, both spectra remained unchanged after removing the light. Illumination with energies greater than 1.8eV at 4K simultaneously increased the N, B and intrinsic defect spectra but, after blocking the light, all 3 signals returned to the pre-illumination level. A model which was based upon excitation to and from the band-edges placed the defect level at 1.1eV above the valence-band edge.

The Level Position of a Deep Intrinsic Defect in 4H-SiC Studied by Photo-Induced Electron Paramagnetic Resonance. M.E.Zvanut, V.V.Konovalov: Applied Physics Letters, 2002, 80[3], 410-2