EFFECTS OF ELECTRIC AND MAGNETIC-FIELDS ON CONFINED DONOR STATES IN A COUPLED DOUBLE QUANTUM-WELL

We have developed a variational formalism to calculate the effects of electric and magnetic fields on confined hydrogenic donor states in asymmetric coupled double quantum well structures. It is demonstrated that an electric field applied along the growth axis can easily shift the electron wave function from one quantum well across the center barrier into the neighboring well, without ejecting the electron from a confined donor state. Depending on donor location in the structure, binding energy can either increase or decrease under the applied electric field, as had been found in the case of single quantum wells, but with significantly greater rates of change in response to the external field. The magnetic field applied along the growth axis of the quantum well structure leads to additional quantum confinement, increasing both the donor binding energies and the transition energy between the Is and 2p+ donor states. Effect of the relative size of the two coupled quantum wells on the donor binding energy is also discussed. Dipole moment and polarizability of the confined donor states are obtained simultaneously as well.