Electronic states at the silicon-silicon dioxide interface

Localized electronic states at the silicon/silicon dioxide interface are reviewed, and the current knowledge of interface states and fixed oxide charges, and how they influence the characteristics of the MOS structure, is summarized. Experimental results on the properties of these two classes of localized states are presented and discussed. General trends of properties over a very extensive amount of data are noted and an overall picture of these states is given. Various phenomenological models for these electronic states are reviewed and critically discussed. It is pointed out that the current understanding of localized states is, in general, far from satisfactory, and a complete picture is lacking. Theoretical efforts on computing the energy levels of these electronic states are summarized. Most of these approaches are based on highly simplified structures, such as a simple unit cell with an atom missing. While they have been moderately successful, more realistic approaches are still needed. Finally, some theoretical techniques are introduced, in the hope that they may have applications to these problems, and the need for more measurements of non-electrical properties of these states is emphasized.