Hot luminescence and Landau-level fine structure in bulk GaAs

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Abstract
Additional peaks in the luminescence spectra of GaAs in a magnetic field in the region around the one-LO-phonon Raman line are reported. Experiments were performed under conditions close to resonance with interband magneto-optical transitions between Landau levels of low electronic quantum number n (n≤3) for magnetic fields ranging up to 11 T. From the magnetic-field dependence of these features, and the fact that for different excitation energies they occur at the same spectral positions on an absolute scale as long as the magnetic field is kept constant, we argue that they are due to hot luminescence from the recombination of the free excitons associated with Landau levels. Magneto-Raman profiles (Raman intensity versus magnetic field) at the one-LO-phonon position were also measured. Fan plots obtained with the two methods coincide and show a characteristic fine structure of fan lines. The components of this multitude of features have separations that are about five times smaller than those of the dominant transitions between heavy-mass levels and electron states, which were considered in previous works on one-phonon magneto-Raman scattering. Since the same transitions between Landau levels are observed in both experiments, the additional features reflect the electronic structure of the magnetically quantized system. A theoretical interpretation of the fine structure is obtained when admixed valence-band states are taken into account.