FEMTOSECOND TIME-RESOLVED PHOTOEMISSION-STUDY OF HOT-ELECTRON RELAXATION AT THE GAAS(100) SURFACE

Time-resolved two-photon photoemission spectroscopy is used to study t he relaxation of hot electrons as a function of excitation energy for a variety of device grade and molecular beam epitaxial grown GaAs(100) surfaces. Relaxation times ranging from tens of femtoseconds to great er than 400 fs are observed depending on the energy of the intermediat e state, the surface quality, and the bulk material quality. This stud y provides detailed information on electron relaxation dynamics in the corresponding energy range and spatial distribution along the surface normal relevant to hot electron transfer processes at interfaces.