Electron paramagnetic resonance was used to examine thermo- and photo-activated interactions between as-grown intrinsic defects and N/B impurities in nominally high-resistivity 4H-SiC which had been produced without intentional V-doping. The electron paramagnetic resonance spectra, recorded in the dark at 4K, revealed either a low concentration of paramagnetic B, N or a C-vacancy-related defect (ID-1). Photo-induced charge transfer between ID-1, and both B and N, was detected. In some samples, illumination with 0.9 to 1.6eV light at 4.2K quenched the ID-1 signal and produced an approximately equal amount of shallow paramagnetic B. Exposure to 1.9 to 2.7eV light restored the ID-1 center and produced shallow paramagnetic N. A model based upon excitation from the band edges, and threshold energies obtained from photo-electron paramagnetic resonance data, placed the ID-1 level at 0.9eV above the valence-band edge. A comparison of these data with those obtained from other samples that exhibited excess B or N impurities suggested the presence of an additional defect that was no more than 0.9eV below the conduction-band edge. This defect could exchange charge with the N donor.

Interactions between Intrinsic Defects and Nitrogen/Boron Impurities in High-Resistivity 4H-SiC - Electron Paramagnetic Resonance Study. V.V.Konovalov, M.E.Zvanut: Journal of Electronic Materials, 2002, 31[5], 351-5