Analysis of near-interfacial SiO2 traps using photon stimulated electron tunneling

Semiconductor/insulator interface states with energy levels above the semiconductor bandgap have so far escaped direct detection. From experiments on the photon stimulated tunneling of electrons at the interfaces of SiO(2) with Si and SiC, direct evidence is provided for the presence of defects with electron binding energy of 2.8 eV relative to the SiO(2) conduction band edge - well above the silicon bandgap. The defects are located in the near interfacial oxide layer, their density being sensitive to the silicon enrichment of SiO(2). A remarkable correlation is observed between the optically stimulated tunneling transitions and the dark conductivity for various oxide layers, revealing the defects discovered as the common origin of trap-assisted electron injection phenomena in SiO(2).