Optical method for the determination of carrier density in modulation-doped quantum wells

An optical method is suggested to determine the concentration of two-dimensional electrons in modulation-doped quantum wells at low and moderate electron densities between ${10}^9$ and $2\times {10}^{11}{\mathrm{cm}}^{-2}.$ The method is based on an analysis of magnetoreflectivity spectra of charged excitons (trions). The circular polarization degree and the oscillator strength of the charged excitons contain information about the density and spin polarization of two-dimensional electron gas. The method is applied to CdTe/(Cd,Mg)Te and ZnSe/(Zn,Mg)(S,Se) heterostructures.