Carrier thermalization in GaAs and InP studied by femtosecond luminescence spectroscopy
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Thermalization of a nonequilibrium distribution of electrons and holes generated by femtosecond photoexcitation is studied in GaAs and InP via spectrally and temporally resolved luminescence. In both materials, a rapid onset of luminescence is observed over a broad spectral range from the bandgap up to 1.7 eV. The data demonstrate the redistribution of both electrons and holes over a wide energy range within 100 fs, even for excitation densities as low as 10(17) cm-3. Equilibration is is dominated by carrier-carrier collisions with scattering rates higher than predicted by theoretical simulations using static screening of the interaction potential. Our Monte-Carlo calculations including dynamical screening via a molecular dynamics scheme account for the experimental results.