The nature of the Si impurity in ultrathin AlAs/GaAs superlattices

Abstract

The electronic properties of n-type and p-type lightly doped (AIAs)n/(GaAs)n(n = 1, 3) superlattices are investigated through a theoretical study using the calculation ofthe total, local and partial density of states by the recursion method in the tight-bindingapproximation. The influence of an impurity located in the bulk, at or near the interface,and on the surface of these systems has been studied. For all cases, the electronic structuresof a substitutional Si atom is qualitatively more similar to that of a group-III atom than to agroup-V atom. The shift of the bottom of the conduction band and the top of the valenceband with different types of doping is discussed. We also report that there is a local fieldwhen a Si atom is located at the interface, which is different for n-type and p-type dopingstructures, and an electronic centre when Si is in the bulk, Furthermore, this paper indicatesdehybridisation of the surface impurity.