EFFECT OF VALLEY-SPIN DEGENERACY ON THE SCREENING OF CHARGED-IMPURITYCENTERS IN 2-DIMENSIONAL AND 3-DIMENSIONAL ELECTRONIC DEVICES

Accurate characterization of charged impurity centers is of importance for electronic devices and materials. The role of valley-spin degener acy on the screening of an attractive ion by the mobile carriers is as sessed within a range of systems from spin-polarized single valley to six valley. The screening is treated using the self-consistent local-f ield correction of Singwi, Tosi, Land, and Sjolander, known as STLS. T he bound electron wave function is formulated in the form of an integr al equation. Friedel oscillations are seen to be influential especiall y in two dimensions that cannot be adequately accounted for by the hyd rogenic Variational approaches. Our results show appreciable differenc es at certain densities with respect tb simplified techniques, resulti ng mainly in the enhancement of the impurity binding energies. The cal culated Mott constants are provided where available. The main conclusi on of the paper is the substantial dependence of the charged-impurity binding energy on the valley-spin degeneracy in the presence of screen ing.