Miniband dispersion and excitonic effects on the optical-spectra of GaAs/AlxGa1-xAs superlattices

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Ultrafast electron transfer in type II GaAs/AlAs superlattices by femtosecond luminescence

Electron transfer from GaAs wells (Gamma wavefunctions) to AlAs barriers (X wavefunctions) in GaAs / AlAs type II superlattices has been studied by time resolved luminescence with femtosecond resolution. Transfer times can be as short as 140 fs for narrow wells and as long as 25 ps for the widest wells. They do not depend appreciably on the barrier thickness. We discuss the possible contribution to the transfer mechanism of state mixing, intervalley scattering and Frolich interaction. Our measurement favors phonon assisted, intervalley type scattering, modified by the overlap of the different wavefunctions

EXCITONS IN SMALL PERIOD GaAs/GaAlAs SUPERLATTICES

L'énergie de liaison de l'exciton dans des super-réseaux GaAs-GaAlAs de petites périodes est déterminée au moyen de l'excitation de la photo-luminescence et de la photoluminescence en fonction de la température. L'énergie de liaison de l'exciton lié au trou lourd décroît avec la période du super réseau. Les résultats expérimentaux sont en accord avec un calcul variationnel.We report the optical determination of exciton binding energies in small period GaAs/Ga0./Al0.3As superlattices by means of low temperature photoluminescence excitation spectroscopy and photoluminescence spectroscopy as a function of temperature. The heavy-hole exciton binding energy decreases with superlattice period. Our experimental findings are in agreement with a variational calculation

Saddle-point excitons in GaAs/GaAlAs superlattices - magneto-optical effects

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Fractional Brownian motion and data traffic modeling: The other end of the spectrum

Journal PaperWe analyze the fractal behavior of the high frequency part of the Fourier spectrum of fBm using multifractal analysis and show that it is not consistent with what is measured on real traffic traces. We propose two extensions of fBm which come closer to actual traffic traces multifractal properties