Photogenerated hot electron dynamics at GaAs (100) surfaces

MBE grown GaAs (100) surface quantum wells were studied using time-resolved two-photon photoemission spectroscopy where the electron distribution was directly determined. Relaxation lifetimes from 50 to 450 fs were measured and were found to be dependent on the energy of the excited electron distribution. Radiative lifetimes at the semiconductor-liquid interface were obtained using time-correlated single-photon counting. From the concentration dependence and other studies, we estimate that the electron transfer cross section is comparable to the molecular cross sections, i.e. electron transfer approaches the adiabatic limit and conditions are optimal for hot electron capture. This work provides parameters to make the hot electron transfer channel competitive with electron relaxation enabling a future generation of solar cells exploiting hot electrons.