Influence of impurities and vacancies on electronic properties of AlAs/GaAs superlattices

Based on the tight-binding approximation (TBA), the electronic structures of short-period AlAs/GaAs superlattices with impurities and vacancies are calculated by Recursion method for the first time. The calculated results of local- and partial-density of states clearly show the local environment of the relatively small amounts of disordered impurities and vacancies in AlAs/GaAs and their influence on the electronic properties of these materials. The positions of new states appeared in the band gap of AlAs/GaAs structures with different point defects are calculated. By the aid of the discussion of atom valence, the authors find that there is an electronic center around a point defect in the bulk and a local field across the interface with an impurity or a vacancy which will induce a slight shift of the charge density. Comparison of the influence between impurity and vacancy on the pure superlattices is given. Furthermore, the authors confirm that the effect of a disordered point defect is highly localized in all cases.EI04243-2521