The Fermi energy and screening length in n-type GaAs

Abstract

The Fermi energy, E F , and the screening length, Q −1 , in heavily doped n-type GaAs are calculated using the impurity band tail density of states derived recently by Sa-yakanit and Glyde. This density of states agrees with Halperin and Lax's result at low energies and can be extended to higher energies. The resulting E F and Q −1 agree well with values computed by Hwang using the Halperin and Lax density plus a somewhat arbitrary extrapolation. Compensation with attractive impurities is also introduced to lower E F and increase its sensitivity to the band tail density of states. However, E F can be lowered only a little without violating the Thomas–Fermi approximation upon which the concept of a screening length is based.