The influence of compressive stress on shallow-donor impurity states in symmetric GaAs-Ga1-xAlxAs double quantum dots.

The effects of compressive stress on the binding energy of shallow-donor impurity states in symmetrical GaAs-Ga1-xAlxAs double quantum dots are calculated variationally using a parameterized wave function within the effective-mass approximation. Results are obtained for different dot and barrier widths, donor ion positions, and compressive stresses along the growth direction of the structure. In the direct-gap regime (for stress values up to 13.5 kbar) the binding energy increases linearly with the stress. In the indirect-gap regime (for stress values greater than 13.5 kbar) and with the donor ion at the center of the dot, the binding energy increases up to a maximum and then decreases. For all donor ion positions, the binding energy shows nonlinear behavior in the indirect-gap regime due to the Γ-X crossing effect. In the limit of single quantum wells, the results we obtain are in good agreement with those previously obtained for the case in which the donor ion is at the center of the well. [ABSTRACT FROM AUTHOR]