Calculations of Energy Levels of Oxygen and Silicon Vacancies at the Si-SiO2 Interface

Abstract

In order to understand physical origins of interface states in St-SiO2 system, calculations of interface band structures on the unreconstructed and oxidized surface of Si are carried out simulating the Si-SiO2 system by silicon surface epitaxially covered with monoatomic oxygen layer. Then modifying the model to include oxygen and silicon vacancies, localized levels associated with the vacancies are calculated using perturbation theory. It is shown that so called surface-states on a clean surface whose density is of the order of 1014 cm-2 are completely removed away from the energy gap of Si under the complete oxidation and that the same number of localized levels exist in the energy gap of Si as that of dangling bonds of Si atom associated with the oxygen and silicon vacancies at the interface.