Excitons in near-surface quantum wells in magnetic fields: Experiment and theory

The exciton transition and binding energies have been investigated in near-surface InGaAs/GaAs quantum wells theoretically and experimentally (by photoluminescence and photoluminescence excitation spectroscopy at 4.2 K). The contribution induced by vacuum has been analyzed for the ground and excited exciton states in perpendicular magnetic fields up to 14 T. The vacuum potential barrier has been shown to increase the magnetoexciton transition energies, (h) over bar omega(n), but nearly not to influence their binding energies, E-n. In contrast, the image charges (caused by the abrupt, one order of magnitude, decrease of the dielectric constant at the semiconductor-vacuum interface) modify the Coulomb interaction and lead to the increase of both (h) over bar omega(n) and E-n. The magnetic field has been found to enhance the contribution of the image charges to the exciton binding energy and to decrease their influence on the transition energy. The effect is due to the in-plane exciton wave function squeezing in a magnetic field. (C) 1998 American Institute of Physics.