Amphoteric defects at the Si-SiO2 interface

Abstract

We have investigated the defects generated at the Si-SiO2 interface by x-ray irradiation and Fowler–Nordheim tunneling. When the positive charge trapped in the SiO2 after tunneling at low temperature is annihilated by photoinjected electrons, equal numbers of acceptorlike and donorlike interface states form. One interface state of each type is produced for each trapped positive charge. Similarly, if some interface states are allowed to form after x-ray irradiation, and then the remaining trapped holes are eliminated by photoinjecting electrons at 90 K, equal numbers of acceptorlike and donorlike interface states remain. The data indicate that each trapped positive charge can produce a single amphoteric center, probably a trivalent silicon interfacial defect. These defects account for all of the interface states observed in this study.