Band-tail parameter modeling in semiconductor materials

An analytical formulation and modeling for determining the band-tail parameter $E_0$ taking into account the carrier-impurity and phonon-carrier interactions and the structural disorder is presented. An analysis of the different contributions to $E_0$ at low and room temperature in $n$- and $p$-type GaAs is also done. The theoretical results agree very well with experiment for noncompensated GaAs samples. The agreement was achieved in a wide range of carrier concentrations at 5 K and room temperature by adding a constant value to $E_0$, lower than 4.1 meV, related to the structural disorder.