Magneto-optics of two-dimensional electron gases modified by strong Coulomb interactions in ZnSe quantum wells

摘要

The optical properties of two-dimensional electron gases in ZnSe/(Zn,Be)Seand ZnSe/(Zn,Be,Mg)Se modulation-doped quantum wells with electron densities upto 1.4x10^{12} cm^{-2} were studied by photoluminescence, photoluminescenceexcitation and reflectivity in a temperature range between 1.6 and 70 K and inexternal magnetic fields up to 48 T. In these structures, the Fermi energy ofthe two-dimensional electron gas falls in the range between the trion bindingenergy and the exciton binding energy. Optical spectra in this regime are shownto be strongly influenced by the Coulomb interaction between electrons andphotoexcited holes. In high magnetic fields, when the filling factor of thetwo-dimensional electron gas becomes smaller than two, a change fromLandau-level-like spectra to exciton-like spectra occurs. We attempt to providea phenomenological description of the evolution of optical spectra for quantumwells with strong Coulomb interactions.