Low-energy density of states tail in heavily doped semiconductor

The problem of the density of states of deep fluctuation levels in a semiconduct or doped by fine donors and acceptors is considered with allowance for Debye screening. The dependence is found of the leading term of the logarithm of the density of states and of the electron localization radius 1/α on ionization energy E, for different values of parameter δ = N$_d$r$_{0}^{4}$/a$_{B}$, where N$_d$ is the donor population, r$_{0}$ is the screening radius, and a$_{B}$ is the Bohr radius of an isolated doping-material atom. It is clarified that the form of the distribution of doping-material electrons in an optimal fluctuation, the potential energy of an electron in an optimal well, and consequently, also the density of states of deep fluctuation levels are highly dependent on the screening radius r$_{0}$.