Hot carrier dynamics near the Fermi edge of n-doped GaAs

Femtosecond bleaching measurement are performed in n-doped GaAs at both 300 K and 14 K using low densities of carriers injected at 2 eV. The dwell time of electrons excited far above the Fermi sea is reduced because of hot-electron/cold-electron interactions. The response at 14 K is much stronger and slower than that at 300 K. This is attributed to: (i) the proximity to the Fermi level of the conduction band states probed via split-off valence band coupling; (ii) slow Landau damping of non-equilibrium plasmons, primarily by the minority holes which then heat the majority electrons.