POLARIZABILITY OF A DONOR IMPURITY IN A GAAS-ALGAAS QUANTUM-WIRE

The polarizability and the ground state binding energy of a donor impu rity located in a semiconductor quantum well wire of rectangular cross -section with finite barrier potential is calculated through the varia tional method. We assume that the donor is located at the center of th e wire and that the electric field is applied in the direction perpend icular to the wire length (z-direction), making an angle theta with th e x-axis. We present our results for the ground state binding energy a s a function of the size of the wire for several values of the electri c field strength and of the angle theta. It is found that the polariza bilities decrease as the wire dimensions (L-x and L-y) decrease, until they reach a minimum at a certain value of L-x (L-y fixed) and then i ncrease as the width becomes smaller. The binding energies and the pol arizabilities, as expected, have a strong dependence on the geometrica l form of the wire and on the angle theta. (C) 1997 Elsevier Science L td.