Photoemission of Electrons from Silicon into Silicon Dioxide. Effects of Ion Migration in the Oxide

Abstract

Photoemission of electrons from silicon into SiO₂ has been used as a tool to study changes at the silicon‐SiO₂ interface which result from the application of high electric fields at elevated temperature. Before treatment the photoemission threshold energy for electrons from silicon into SiO₂ is 4.22 eV. After applying a dc voltage across the oxide at elevated temperature, with polarity such that the silicon is negative, there are significant changes in the photoemission spectrum. A new low‐energy branch appears which gives a threshold energy around 3.05 eV. This is believed to be due to the formation of a degenerate n‐type surface. Light absorption by electrons in the conduction band becomes important, and there is a corresponding contribution to the photoemission current. Semiquantitative arguments are advanced to show what the charge distribution in the oxide must be to account for the experimental results.