The role of nonequilibrium carriers in linear charge transport (Ohm’s law)

Abstract

The charge transport in a bipolar semiconductor to a metal wire was studied in a linear approximation with respect to the electric field. It is shown that both electrons and holes in general are nonequilibrium carriers in an arbitrarily weak electric field. Therefore, the consideration of surface and bulk recombination is necessary for the correct description of electrical conductivity. The spatial distributions of quasi-Fermi levels for electrons and holes are obtained in the quasi-neutrality approximation, and the general expression for a bipolar semiconductor conductivity is derived. This conductivity depends strongly not only on the transport of electrons and holes but also on the surface-and bulk-recombination rates. The criteria of low and high rates of recombination are determined; it is shown that a commonly used expression for the conductivity of a bipolar semiconductor is valid only at high rates of surface and/or bulk recombination.