Experiments on the photon-stimulated tunnelling of electrons at the interfaces of SiO2 with Si and SiC revealed the presence of defects with an electron binding energy of 2.8eV, relative to the SiO2 conduction band; well above the semiconductor band-gap. These defects, which had not been detected directly, were located near to interfacial oxide layers and their density was sensitive to Si enrichment of the oxide. These defects were suggested to be the cause of a trap-assisted electron injection phenomenon.

V.V.Afanasev, A.Stesmans: Physical Review Letters, 1997, 78[12], 2437-40