Semiconductor Electrodes: VII . Digital Simulation of Charge Injection and the Establishment of the Space Charge Region in the Absence and Presence of Surface States

Abstract

Transport of free carriers following charge injection to a semiconductor electrode is simulated. The relaxation of the free carrier results in the buildup of the space charge region whose properties are calculated. For an intrinsic semiconductor, the relaxation resembles that of the cations and anions in the diffuse double layer at a metal/electrolyte interface following charge injection to the metal. For an extrinsic semiconductor, some additional specific effects arise, which are discussed. The effect of surface states is considered and the interaction of a surface level with the semiconductor bands is simulated. This interaction results in trapping of charge from the space charge region and delivery of it to the surface. The properties of the space charge region in the presence of surface states are calculated, and their effect on the relaxation process demonstrated.