The characteristic features of photo-current and electron paramagnetic resonance spectra were attributed to the principal defects within the gap of optical-quality chemical vapor deposited samples. A shoulder in the photo-current spectra, with an onset at about 2.2eV, was attributed to the single substitutional N defect (g = 2.0024). A second feature in the photo-current spectra, with an onset of about 1.3eV, was observed in as-grown samples with a H-terminated surface. The defect level which was associated with this feature was H-related. This defect disappeared after oxidation of the sample surface. An electron paramagnetic resonance g-value of 2.0028 was also suggested to be H-related.

M.Nesládek, L.M.Stals, A.Stesmans, K.Iakoubovskij, G.J.Adriaenssens, J.Rosa, M.Vanecek: Applied Physics Letters, 1998, 72[25], 3306-8