ELECTRIC-FIELD EFFECTS ON THE STATES OF A DONOR IMPURITY IN RECTANGULAR CROSS-SECTION VACUUM GAAS VACUUM QUANTUM-WELL WIRES

We present a study of the role of the electric field on the binding en ergy 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 s ymmetry axis of the wire. Using the effective-mass approximation withi n a variational scheme we calculate the binding energy of the Is-like ground state as well as that of some excited states (2s-, 2p(x)-, and 2p(z)-like) as a function of the geometry, applied electric field, and donor-impurity position. We found that the presence of the electric f ield breaks down the degeneracy of states for impurities symmetrically positioned within the structure, and that the geometric confinement a nd the electric field are determinant for the existence of bound excit ed states in these structures. Future interpretations of optical pheno mena related with shallow donor impurities in vacuum/GaAs/vacuum QWWs, in which the effects of an applied electric field competes with the q uantum confinement, must take into consideration these results. (C) 19 98 American Institute of Physics.