Current-voltage characteristics of Schottky barrier diodes with dynamic interfacial defect state occupancy

Schottky barrier diode theory conventionally assumes that the barrier height remains constant with the applied bias. However, high ideality factors and certain anomalous capacitance-voltage characteristics can only be explained by letting the barrier height vary with the applied voltage. Changes in the occupation of surface states have been inferred to be the cause of this change in barrier height, although the precise nature of these surface states has not yet been determined. This article examines the role of monoenergetic interfacial defect states whose occupancy is dynamically controlled by the local carrier densities, rather than by equilibrium conditions. Certain types of surface donor and acceptor states are shown to have a strong influence on the resulting current-voltage characteristics. The Al/GaAs(100) system is discussed in detail and experimental results are compared to this analytic model.