Photoluminescence from hot carriers in low-temperature-grown gallium arsenide

Abstract

Band-to-band photoluminescence spectra of GaAs grown at 200 °C by molecular beam epitaxy have been measured as a function of lattice temperature (10<TL<290 K), laser photon energy (1.62<Ep<2.07 eV) and excitation intensity during 5 ps excitation. Carrier recombination, previously reported to be as fast as 300 fs in this material, displays at most a weak density dependence, consistent with a monomolecular mechanism. The spectra correspond to quasi-steady-state carrier distributions which evolve from nonthermal to thermal character as the density increases from 1016 to 1018 cm−3. For the thermal distributions, the characteristic temperature depends strongly on Ep; values near 1000 K are obtained for Ep≳1.85 eV. The results are related to ultrafast carrier recombination, intervalley transfer, and thermalization.