Electric field effect on the donor levels bound to the X-valleys in AlAs/GaAs quantum wells

We study the Si donor states bound to X-valleys in a GaAs/AlAs/GaAs layer system in the presence of the electric field using a simple Koster-Slater impurity model. The multilayer structure is modeled with the spds⁎ tight binding approximation and the impurity is described by a single site potential. By analyzing the local density of states we have obtained the values of the binding energies of impurity levels bound to “parallel” Xz and “perpendicular” Xx,y valleys (with respect to the direction of the electric field) as function of barrier width and impurity position in the barrier for various values of the electric field. For the case of zero electric field we have obtained very similar results to the k·p calculations in Carneiro and Weber [1].