Combined optical-microwave study of electron-exciton dynamic processes in undoped GaAs/AlGaAs quantum wells

Microwave radiation (36 GHz) absorption by photogenerated electrons is comb ined with photoluminescence (PL and its excitation (PLE) spectra in order t o study electron-exciton dynamics under low photoexcitation intensity in un doped GaAs/AlGaAs quantum wells. The excitation spectra of the photoinduced microwave absorption (PMA) and the PLE spectra are modified with increasin g the lattice temperature from 2 up to 80 K. The observed spectral variatio ns are analyzed using a rate equations model that is based on the main gene ration-recombination and dissociation processes governing the electron and exciton dynamics. We find that the temperature dependence of the PMA excita tion spectrum can be well accounted for by assuming both thermal and non-th ermal, Auger-like exciton dissociation mechanisms. The model fitting yields an estimate of the rate coefficients for the exciton formation and dissoci ation processes.