PHOTOGENERATED HOT-ELECTRON DYNAMICS AT GAAS (100) SURFACES

MBE grown GaAs (100) surface quantum wells were studied using time-res olved two-photon photoemission spectroscopy where the electron distrib ution was directly determined. Relaxation lifetimes from 50 to 450 fs were measured and were found to be dependent on the energy of the exci ted electron distribution. Radiative lifetimes at the semiconductor-li quid interface were obtained using time-correlated single-photon count ing. From the concentration dependence and other studies, we estimate that the electron transfer cross section is comparable to the molecula r cross sections, i.e. electron transfer approaches the adiabatic limi t and conditions are optimal for hot electron capture. This work provi des parameters to make the hot electron transfer channel competitive w ith electron relaxation enabling a future generation of solar cells ex ploiting hot electrons.