Donor binding energies and spin-orbit coupling in a spherical quantum dot

The ground state and a few excited state energies of a hydrogenic donor in a spherical quantum dot (GaAs in a GaAlAs matrix) are computed. While the 1s and the 2s-state energies behave normally for dots of all radii, the 2p(0) and 2p(+/-) states are unbound for most of the radii of interest. It is predicted that a semiconductor quantum dot with a hydrogenic donor will exhibit photoconductivity for a low threshold wavelength similar to12 mum. The spin-orbit coupling gives a contribution of the order of 10(-5) meV for both 2p(0) and 2p(+/-) states. (C) 2004 Published by Elsevier Ltd.