Depolarization and exciton-like shifts in modulation-doped single rectangular and diffusion-modified quantum wells under uniform electric fields

Abstract

Energy levels in the modulation-doped single rectangular and diffusion-modified quantum wells Al 0.3Ga 0.7As/GaAs are obtained using the Kohn and Sham density funclional theory (DFT). The generalized DFT which uses a screened exchange potential in the local density approximation has been used to improve the accuracy of the energies and wavefunctions in these wells. The energy difference between the first excited state and the ground state has been studied in the presence of combined photon and electric fields for two wells with well widths of 70 Å and 100 Å. The energy difference is found to increase as a result of the depolarization and exciton-like shifts when there is no external bias. Under the electric field the shift in the energy difference decreases due to the vanishing of the exciton-like effect. The results obtained within the conventional Kohn and Sham DFT and within the generalized DFT are found to be the same for the well with a width of 100 Å. However, the results obtained from these two schemes are found to be different when the well width is 70 Å.