Above-barrier excitons: first magnetooptic investigation

An above-barrier localized excitonic state in a Bragg confining semiconduct or superstructure based on an (In, Ga)As/GaAs heterosystem is observed expe rimentally. A sharp excitonic resonance corresponding to the interference m echanism of localization is observed in the absorption spectrum of this str ucture at 1.548 eV, i.e., 33 meV above the energy of a bulk exciton in GaAs . The oscillator strength of the above-barrier exciton is twice that of the main excitonic state in the system, and the above-barrier exciton gives ri se to sharp Landau oscillations in the magnetoabsorption spectra. (C) 1999 American Institute of Physics. [S0021-3640(99)01110-X].