METAL–INSULATOR TRANSITION IN A QUASI-LOW-DIMENSIONAL SEMICONDUCTOR SYSTEM

Abstract

Metal–Insulator transition using exact quasi dielectric functions is investigated for a shallow donor in an isolated well of GaAs/Ga 1-x Al s As superlattice system within the effective mass approximation. Vanishing of the donor ionization energy as a function of well width and the donor concentration suggests that no transition is possible below a well width of 50 Å supporting the scaling theory of localization. The effects of Anderson localization, exchange and correlation in the Hubbard model are included in a simple way. The relationship between the present model and the Mott criterion in terms of Hubbard model is also brought out. The critical concentration is enhanced when a random distribution of impurities is considered. Results are compared with the existing data available and discussed in the light of existing literature.