A theory of the electronic transport properties of contacts between two dissimilar semiconductors is presented, which includes the effects of biashyphen;dependent interface state charge on the electrostatic potential distribution in the contact. The quasihyphen;Fermi level for the interface states is determined by the competition between the capture of electrons and holes at the interface for a given bias voltage. The conditions for diffusionhyphen;limited or thermionichyphen;emissionhyphen;limited current flow are defined in terms of heterojunction parameters and material properties. Ignoring the direct recombination currents through interface states, the interface states have no effect on diffusionhyphen;limited current, but when the transport is limited by the thermionic emission of carriers there are pronounced electrostatic effects on this current from interface states. A limiting density of interface states sim;1011ndash;1012cmminus;2thinsp;eVminus;1has been established above which the currenthyphen;voltage (Jhyphen;V) relations are independent of the parameters characterizing these states, and for this condition thenast; value of the exponentialJhyphen;Vcharacteristics is quest;2 over an appreciable range of bias voltage.
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