OBSERVATION OF RESONANT EXCITON COOLING IN GAAS ALGAAS MULTIPLE-QUANTUM-WELL STRUCTURES/

In this paper we report detailed low temperature (6 K) photoluminescen ce excitation spectra of GaAs/AlGaAs multiple quantum well structures while monitoring the intensity of the recombination due to n = 1 elect ron/heavy hole 1S and 2S excitons. The excitation spectra over the reg ion of interest of the 1S exciton recombination, apart from some previ ously observed exciton absorption peaks, are flat. Whereas, the excita tion spectra of the 2S exciton recombination exhibit some previously u nreported decreases in the luminescence intensity. We ascribe these di ps to a reduction in the effective 2S exciton temperature and thus the 2S exciton luminescence intensity. The reduction in the 2S exciton te mperature at the particular excitation photon energies of the dips is caused by the selective creation of excitons in the continuum and the subsequent emission of one or two LO phonons resulting in 1S excitons with K similar to 0. (C) 1997 Elsevier Science Ltd