EXCITONS IN NEAR-SURFACE QUANTUM-WELLS - LOCAL PROBE OF SEMICONDUCTORVACUUM SURFACE/

We have investigated experimentally (by photoluminescence and photolum inescence excitation spectroscopy at 4.2 K) and theoretically the grou nd and excited exciton states in near-surface InGaAs/GaAs quantum well s (QWs) in perpendicular magnetic fields up to 14 T. The evolution of the exciton states in the magnetic field and with the decrease of thic kness of the cap barrier layer between the QW and vacuum has been show n to be strongly influenced by the high vacuum potential barrier and b y the abrupt, one order of magnitude. decrease of the dielectric const ant on the semiconductor/vacuum surface. The peculiarities of the Star k effect in a perpendicular near-surface electric field have been anal yzed. These effects can be used for the local probe of the near-surfac e electric field.