Magnetic Freezeout and Band Tailing inn−InAs

The temperature and magnetic field dependence of the Hall coefficient of $n-\mathrm{I}\mathrm{n}\mathrm{A}\mathrm{s}$ have been measured in static magnetic fields up to 210 kG over the interval 0.5-4.2 K. We have observed magnetic freezeout in three samples with excess donor concentrations $(N_D-N_A)=9.\mathrm{}5\times {10}^{15},1.1\mathrm{}\times {10}^{16},\mathrm{and} 1.8\times {10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$. A new result of these experiments is the evidence that Gaussian-like tails are present on the densities of states of the conduction band and impurity level. These tails are due to random fluctuations in the impurity density. The extent of this band tailing was determined from the experimental data and the theory of Dyakonov, Efros, and Mitchell. However, to explain the observed activation energy and its temperature dependence it was necessary to develop a model based on the existence of localized states deep in the conduction-band tail.