Density dependence of radiative and nonradiative recombination rates in a gatedGaAs/Ga1−xAlxAsmodulation-doped quantum well

The recombination time of photoexcited carriers is measured by picosecond luminescence experiments in a $\mathrm{GaAs}/{\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ modulation-doped quantum well at low temperature. The electron density is varied in the 0-3×${10}^{11}$ ${\mathrm{cm}}^{-2\mathrm{}}$ range by the use of a Schottky gate. These results, combined with a measurement of the variation of the photoluminescence efficiency, evidence a decrease of the radiative rate and an increase of the nonradiative rate with increasing electron density.