Femtosecond luminescence spectroscopy of carrier thermalization in GaAs and InP
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Thermalization of a non-equilibrium 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 dominated by carrier-carrier collisions with scattering rates that are considerably higher than predicted by theoretical simulations using static screening of the interaction potential. Our Monte Carlo calculations, applying a molecular dynamics scheme, give enhanced scattering among the carriers with respect to a static screening approach, resulting in smoother distribution functions and luminescence spectra which are in good agreement with the experimental results.