Oscillator strength of trion states in ZnSe-based quantum wells

The oscillator strength of negatively charged excitons (trions) in ZnSe/(Zn,Mg)(S,Se) quantum-well structures with n-type modulation doping is studied by means of reflectivity as a function of electron concentration, temperature, and external magnetic fields. The trion oscillator strength is found to increase linearly with increasing electron concentration up to $6\times {10}^{10}{\mathrm{cm}}^{\mathrm{-}2}.$ The trion nonradiative damping shows no dependence on the electron concentration or external magnetic field. An optical method, based on the analysis of the polarization of the trion line, is proposed to investigate two-dimensional electron gases of low density from ${10}^9$ up to ${10}^{11}{\mathrm{cm}}^{\mathrm{-}2}.$