Negatively charged trion in ZnSe single quantum wells with very low electron densities

The polarization- and excitation-intensity-dependent photoluminescence of t he negatively charged trion is investigated for ZnSe single quantum wells e mbedded in ternary and quaternary barriers. The measurements were performed in magnetic fields up to 11.8 T perpendicular to the quantum well. The spi n-singlet state of the trion is clearly identified. In contrast to GaAs qua ntum wells, the increase of the trion binding energy through the magnetic f ield is found to be negligible, which is explained by the relatively small spatial extent of the trionic wave function in wide-band-gap materials. For magnetic fields beyond 7 T a resonance becomes stabilized that is identifi ed as excited trion spin-triplet state because of its anticorrelation with the trion spin-singlet state behavior for increasing excitation energy.