Band diagrams at intimate metal/n-semiconductor interfaces, according to the fixed-separation model of interface gap states. Gap states are assumed to be positioned at a fixed distance away from the atomic MS interface. The two drawings are for (a) negatively charged gap states and (b) positively charged gap states. In (b), the thin barrier between the metal and the gap states is assumed to be transparent to electrons by tunneling, and therefore has no effect on the electrical transport properties of the Schottky barrier. This model is frequently used to analyze effects due to metal induced gap states or defect states.