Experimental and theoretical investigation of nonradiative broadening excitation spectra of GaAs/AlGaAs quantum wells under magnetic field in Faraday geometry

Exciton excited states in the quantum well are studied by measuring reflectance spectra with additional tunable laser excitation. The nonradiative broadening of the ground exciton state in the reflectance spectrum shows a significant change when a laser resonantly excites exciton states. Applying magnetic field up to 6 T, we could trace the formation of Landau levels and evolution of the exciton states of size quantization in a 14-nm GaAs/AlGaAs quantum well. Sensitivity of the technique allowed for observation of the second exciton state of size quantization, unavailable for conventional reflectance and photoluminescence spectroscopy. Our interpretation is supported by the numerical calculation of the exciton energies of the heavy-hole and light-hole subsystems. The numerical problems were solved using the finite-difference method on the nonuniform grid. The ground Landau level of the free electron–hole pair was observed and numerically analyzed. In addition to energies of the excited states, electron–hole distances and exciton–light interaction constants were investigated using the exciton wave functions obtained in numerical procedure.