The photon-stimulated tunnelling of electrons at Si/SiO2 and SiC/SiO2 interfaces was shown to be insensitive to the density and the energy distribution of electrons. The observed relationship of photon-stimulated tunnelling to the type of oxide layer revealed a defect level in the oxide. The energy level of the defect was located at 2.8eV below the conduction band of SiO2. The defect density increased with Si enrichment of the SiO2. An observed correlation, between the photon-stimulated tunnelling yield and the dark conductance of the oxide, suggested that the isolated defect states were involved in the high-field electron transport of SiO2 layers.

V.V.Afanasev, A.Stesmans: Journal of Physics - Condensed Matter, 1997, 9[6], L55-60