INFLUENCE OF LIGHT ON THE CONFINEMENT POTENTIAL OF GAAS ALXGA1-XAS HETEROJUNCTIONS/

The energy levels of confined subbands in very-high-mobility GaAs/AlxG a1-xAs heterostructures are experimentally determined using the resona nt coupling between the electric subbands and Landau levels that occur s in tilted magnetic-field measurements. Theoretical subband energies are calculated self-consistently taking into account wave penetration into the barrier and exchange effects. A comparison between theory and experiment enables the shape of the confinement potential to be deter mined for these samples which are extensively used in studies of the f ractional quantum Hall effect and possible Wigner crystallization. Ill umination of the samples with light whose energy is greater than the b and gap of the AlxGa1-xAs is shown to dramatically affect the shape of the confinement potential and cause large reductions in carrier densi ty for continuous illumination.