EVIDENCE FOR A BAND TAIL ON THE CONDUCTION BAND EDGE OF THERMAL SiO2 FROM PHOTON ASSISTED TUNNELING MEASUREMENTS

Abstract

Photon assisted tunneling measurements of electrons at the Al/SiO2 interface have been extended into the range 0.4 eV ≥ ϕ ≥ 0.1 eV, where ϕ = ϕB-hv is the effective tunneling barrier, ϕB is the Al/SiO2 barrier height and hv is the incident photon energy. When the effective barriers are smallest, the tunneling characteristics correspond to anomalously high barriers, i.e. ϕB seems to increase with photon energy. This apparent anomaly can be resolved with the assumption that a band tail of 0.1 eV exists on the SiO2 conduction band edge.