Hydrogenic donor impurity states of quantum ring in the presence of an electric field

Using a variational approach within the effective mass approximation, we calculated the ground state binding energy of a donor impurity of the GaAs quantum ring (QR) in the presence of an electric field. The donor impurity binding energy as a function of the QR structure parameters (the radial thickness, the height), the impurity position and the applied electric field is investigated. The main results can be summarized as follow: 1) The donor binding energy decreases gradually as the QR structure parameters increase in the infinite confinement potential; 2) With increasing the applied electric field strength, the donor binding energy decreases gradually; 3) The donor binding energy firstly increases, and then decreases as the impurity moves from the bottom of the QR to the top along the z axis direction of the QR, indicating that there is a maximum; 4) The donor binding energy exhibits a maximum as the impurity position moves from the internal surface of the QR to the external surface.