D- STATES IN GAAS/ALXGA1-XAS SUPERLATTICES IN A MAGNETIC-FIELD

The states of a negative donor center (D-) located at the center of a quantum well (QW) of a GaAs/AlxGa1-xAs superlattice are investigated theoretically in a magnetic field applied along the growth axis. The energy levels of the ground (singlet 1s,1s;s) state and four excited (triplet 1s,2p;t states and the singlet 1s,2p;s) state of the D- center are obtained as functions of the magnetic field. The calculation is based on a variational approach in which we use trial wave functions with six variational parameters. We have investigated the influence of the following effects on the energy of the D- states: (1) tunneling of the electrons into the adjacent wells of the superlattice, (2) electron-electron (e-e) correlation, and (3) the electron-phonon interaction. The magnetopolaron effect on these energies is studied within second-order perturbation theory. A detailed comparison is made between our theoretical results and available experimental data which are interpreted as transition energies between the D- states. The effect of band nonparabolicity is of minor importance for most of the transition energies except for the transition from the D- ground state to the 1s,2p+;s state at high magnetic fields. © 1995 The American Physical Society.