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 disor dered semiconductors. In particular, assuming Fermi-Dirac statistics and ch arge neutrality, we determine how the Fermi level position varies with temp erature for various amounts of disorder and various dopant concentration le vels, disorder being represented by the breadth of the tails in the conduct ion band and valence band distributions of electronic states. We find that as the disorder is increased the Fermi level is pulled towards the intrinsi c Fermi level. An explanation for this result is provided. (C) 2000 America n Institute of Physics. [S0021-8979(00)02319-7].