In this work, we perform a theoretical study, of the binding energy of the ground state of a hydrogenic donor impurity in a vertical-coupled quantum-dot structure. We have considered the effects of hydrostatic pressure and external applied electric field and we have used a variational method and the effective mass approximation. The low dimensional structure consists of three cylindrical shaped GaN quantum-dots, grown in the z-direction and separated by Al_xGa_1-xN barriers. Our results are reported for several sizes of the structure (well width, barrier thickness, and dot radius), and takes into account the strong built-in electric fields caused by the piezoelectricity and spontaneous polarizations [1,2], the variation of the impurity position along the z-direction, the effect of external applied electric field, and hydrostatic pressure. We have found that, for both, symmetrical and asymmetrical dimensions of the structures, the binding energy, as a function of the impurity position, has a similar behavior to what is shown by the electron wave function without the Coulomb interaction. Additionally, it is obtained that the presence of the electric field changes dramatically the profile of the binding energy, destroying (favoring) the symmetry in symmetric (asymmetric) structures. Regarding the effect of hydrostatic pressure, our results show that the binding energy increases due to the increasing of the Coulomb interaction mainly related to changes with the hydrostatic pressure of the dielectric constant. Also, depending on the impurity position, the binding energy can increase or decrease with the hydrostatic pressure mainly due to increases or decreases of the carrier-wave function’s symmetry.

[1] C. X. Xia, S. Y. Wei, and X. Zhao, Applied Surface Science 253, 5345 (2007).

[2] C. Xia, F. Jiang, and S. Wei, Superlattices and Microstructures 44, 121 (2008).

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1. Calculation of direct and indirect excitons in GaAs/Ga_1−xAl_xAs coupled double quantum wells: electric and magnetic fields and hydrostatic pressure effects
2. Hydrostatic pressure and Γ − X mixing effects on the exciton and impurity related optical properties in GaAs-Ga_1−xAl_xAs quantum wells