Impurity band structure in lightly doped semiconductors

The density of states and the position of the Fermi level in the impurity band at zero temperature have been studied by Monte Carlo computer simulation over a wide range of degrees of compensation. The impurity concentration is thought to be so small that the electron states of the impurity band are localised. The density of states has a soft Coulomb gap in the vicinity of the Fermi level, and its behaviour in this region is shown to have a universal character. In the cases of extremely small and extremely close compensation the simulation results agree with the theoretical ones obtained earlier. The increase in the activation energy epsilon ₁ of the band conductivity at high degrees of compensation is computed and agrees with the experimental results. However, the computed value of hopping conductivity activation energy epsilon ₃ is four times as large as the experimental one.