The dependence of the Fermi level on temperature, doping concentration, and disorder in disordered semiconductors

We employ an elementary model for the distribution of electronic states to develop a quantitative theory of equilibrium occupation statistics in disordered semiconductors. In particular, assuming Fermi-Dirac statistics and charge neutrality, we determine how the Fermi level position varies with temperature for various amounts of disorder and various dopant concentration levels, disorder being represented by the breadth of the tails in the conduction band and valence band distributions of electronic states. We find that as the disorder is increased the Fermi level is pulled towards the intrinsic Fermi level. An explanation for this result is provided. (C) 2000 American Institute of Physics. [S0021-8979(00)02319-7].