Reconstructing states at the Si–SiO2 interface

There has been a continued interest in the microscopic nature of the Si–SiO2 interface of the thermally oxidized silicon system. Charges and states near the interface often determine the electronic properties of metal–oxide–semiconductor devices, and hence it is of paramount importance to obtain a detailed understanding of the interfacial electronic structure. We have considered the role of interface states in the semiconducting gap arising from threefold coordinated Si atoms as well as strained Si–Si bonds. The obtained reconstructing character of these interface states has interesting implications for the electronic and optical properties of the interface. In particular, within our model one is able to understand qualitatively and semiquantitatively results of many experimental investigations of the Si–SiO interface. These include the amphoteric, metastable character of the interface states, the anomalous hole trapping cross sections and processes at the interface, and the dependence of the shape of the interface density of states on the conductivity type of the silicon substrate.