Electric field effects on the states of a donor impurity in rectangular cross-section vacuum/GaAs/vacuum quantum-well wires

Abstract

We present a study of the role of the electric field on the binding energy of the ground and first few excited states of a shallow impurity in a rectangular cross-sectional area vacuum/GaAs/vacuum quantum-well wire (QWW), where the electric field is applied perpendicular to the symmetry axis of the wire. Using the effective-mass approximation within a variational scheme we calculate the binding energy of the 1s-like ground state as well as that of some excited states (2s-, 2px-, and 2pz-like) as a function of the geometry, applied electric field, and donor-impurity position. We found that the presence of the electric field breaks down the degeneracy of states for impurities symmetrically positioned within the structure, and that the geometric confinement and the electric field are determinant for the existence of bound excited states in these structures. Future interpretations of optical phenomena related with shallow donor impurities in vacuum/GaAs/vacuum QWWs, in which the effects of an applied electric field competes with the quantum confinement, must take into consideration these results.