  Ballistic electron emission microscopy (BEEM) was performed to obtain
nanoscale current versus bias characteristics of non-epitaxial Au on p-type
GaAs in order to accurately measure the local Schottky barrier height. Hole
injection BEEM data was averaged from thousands of spectra for various metal
film thicknesses and then used to determine the attenuation length of the
energetic charge carriers as a function of tip bias. We report the marked
increase in attenuation length at biases near the Schottky barrier, providing
evidence for the existence of coherent BEEM currents in Schottky diodes. These
results provide additional evidence against the randomization of a charge
carrier's momentum at the metal-semiconductor interface.
