Measurement of hot-electron scattering processes at Au/Si(100) Schottky interfaces by temperature-dependent ballistic-electron-emission microscopy

Ballistic-electron-emission microscopy measurements have been performed on (Formula presented)-type Au/Si(100) interfaces for injection energies up to 1.2 eV over a range of Au overlayer thicknesses from ∼65 to ∼340 Å at both room temperature and 77 K. Hot-electron attenuation lengths in the Au overlayer have been determined to be 133±2 Å at room temperature and 147±6 Å at 77 K over the energy range of 0.92-1.20 eV above the Fermi level. The lack of energy dependence and the relatively small temperature-dependent change in the attenuation lengths that have been measured indicate that electron scattering with defects is the dominant mechanism affecting hot-electron transport in these Au overlayers. The ratio of the zero-thickness collection current at 77 K to that at room temperature has been measured to be 1.79±0.09. This large increase in the collection efficiency at 77 K is attributed primarily to the large temperature dependence of the transverse acoustic-phonon population in Si. Images with significant reductions in the collection current at topographic locations that have a large surface gradient have been obtained at room temperature. Calculations, which assume that the probability of transmission across the interface is independent of the transverse momentum of the electron, correlate well with the experimentally observed reductions. This result indicates that the injected electrons remain forward focused with little broadening as they pass through the Au overlayer, which implies that elastic scattering at the Au/Si interface accounts for the observation from previous Au/Si ballistic-electron-emission microscopy studies that transverse momentum is not conserved.