Dielectric Enhancement and Mobility ofα−Sn

Abstract

The static dielectric function $\epsilon \mathrm{}\left(q\right)\mathrm{}$ for degenerate $n$-type $\alpha -\mathrm{S}\mathrm{n}$ has been calculated for small $q$. Owing to the fact that the degeneracy of the contact point between the conduction and valence bands is symmetry induced, the dielectric constant has a strong dependence on impurity concentration and is greatly enhanced in value for low-doping concentrations. This dielectric enhancement gives an excellent quantitative account of the observed high-mobility values at low temperature (4.2 °K).