Density of states and energy spectra of hydrogenic impurities in quantum-well wires

We calculate binding energies and densities of states of hydrogenic impurities in quantum-well wires with rectangular cross sections using a variational procedure within the effective-mass approximation. Calculations were performed as functions of the position of the impurity in a quantum-well wire of infinite depth and for various sizes of the wire cross section. The center of gravity of the impurity band and the density of impurity states are analyzed and compared with their quantum-well counterparts, with similarities as well as differences being discussed. Our results indicate that a proper consideration of the density of impurity states may be of relevance in the interpretation of future experimental data related to shallow impurities in quantum-well wires.