INTERFACE STATE BAND BETWEEN GAAS AND ITS ANODIC NATIVE OXIDE

The basic interface properties of GaAs metal-oxide-semiconductor (MOS) structures formed using an anodic oxidation process in a mixed solution of glycol and water (the AGW process) were investigated. Detailed measurements of the capacitance-voltage and conductance-voltage characteristics and the transient behaviour of the thermal and optical MOS capacitance revealed various anomalies which are not encountered in the silicon MOS system. On the basis of an analysis of such anomalies an interface state band (ISB) model is presented for the GaAs-anodic oxide MOS system, and the origin and properties of the ISB are discussed. The present ISB does not pin the surface Fermi potential but severely limits the range of its movement at steady state to the lower half of the energy gap. © 1979.