Properties of solid state devices with mobile ionic defects. Part I: The effects of motion, space charge and contact potential in metal|semiconductor|metal devices

The characteristics of solid state devices based on p-type semiconductors with mobile acceptors are discussed. The devices are basic ones of the form: metal|semiconductor|metal. The metal electrodes are assumed to be chemically inert and to block material exchange. The effect of the contact potentials as well as of the space charge are taken into consideration. The distribution of charge carriers (holes and acceptors) and the I–V relations are evaluated. These results are compared with those of a model in which the acceptors are immobile and with two approximations in which neutrality is assumed either at the boundary or throughout the whole semiconductor. The motion of the acceptors is found, in some cases, to introduce only minor changes in the I–V relations. This finding may be of significance for solid state devices of reduced scale. The I–V relations of samples much thicker than the equilibrium Debye length reduce to the ones obtained assuming local neutrality throughout the sample. The results also depend significantly on the reaction constant between the acceptors and holes to form neutral acceptors.