BEHAVIOR OF EXCITONIC LEVELS IN SYMMETRICAL AND ASYMMETRIC DOUBLE-QUANTUM WELLS IN A MAGNETIC-FIELD

We studied, theoretically, the excitonic energy levels and the optical absorption spectra for double quantum wells, both symmetric and asymm etric, in the presence of a homogeneous magnetic field. Within the eff ective-mass approach, we expanded the excitonic wave function, in an o rthogonal basis formed by the products of electron and hole wave funct ions in growth direction z, and one-particle solutions of the magnetic Hamiltonian in the x-y plane. We applied our method to the case of Al xGa1-xAs, for which we showed how the exciton wave functions vary, and how the basis functions are mixed in a nontrivial way by the effect o f the Coulomb potential. By taking into account all the mixing between the elements in our base, we Set anticrossings between excited excito nic states (to the best of our knowledge) not reported previously. The behavior in the excitonic energies and wave functions for different w ells and barrier geometries is of importance in double quantum well de vices. (C) 1998 American Institute of Physics.