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 experimentall y (by photoluminescence and photoluminescence excitation spectroscopy at 4.2 K). The contribution induced by vacuum has been analyzed for th e ground and excited exciton states in perpendicular magnetic fields u p 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 ome ga(n) and E-n. The magnetic field has been found to enhance the contri bution of the image charges to the exciton binding energy and to decre ase their influence on the transition energy. The effect is due to the in-plane exciton wave function squeezing in a magnetic field. (C) 199 8 American Institute of Physics.