Binding energies for an exciton (X) trapped in a two-dimensional quantum dot (QD) by a negative ion located on the z-axis at a distance from the dot plane are calculated by using the method of few-body physics. This configuration is called a barrier (A(-), X) center. The dependence of the binding energy of the ground state of the barrier (A(-), X) center on the electron-to-hole mass ratio for a few values of the distance d between the fixed positive ion on the z-axis and the dot plane is obtained. We find that when d --> 0, the barrier (A(-), X) center does not exist in any bound state. We also studied the stability and binding energy of the ground state of the barrier (A(-), X) center in a parabolic QD as a function of the distance d between the fixed positive ion on the z-axis and the dot plane. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 18]
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