Electronic properties of the SiSiO2 interface as a function of oxide growth conditions. II. Fixed charge

Silicon dioxide thermally grown on a silicon substrate contains some trapped charge depending mainly on the conditions of the last treatment. The charge density increases as the square root of oxygen pressure and decreases with temperature. These results are interpreted on the basis of a heterojunction model. Fixed positive charge comes from ionized donor centres each one being associated with an interstitial oxygen molecule. As oxygen solubility reaches a saturation and varies with underlying silicon orientation, it is supposed that a fixed charge lies within some transition layer intermediate between silicon and its oxide. The structure of this layer should depend on silicon orientation and sample history.