Abstract
Ballistic electron emission spectroscopy (BEES) was used to determine the electron barrier height at the interface of Au and an oxidized GaAs film. Two thresholds were observed in the spectra. In a two-step procedure, we identified the first threshold at similar to 1.4 eV, which we show arose from electron-hole pairs excited by photons emitted during scanning tunneling microscopy (STM), and the second threshold at similar to 3.55 eV, which is attributed to the Au/oxidized-GaAs barrier. Our results demonstrate that the two-threshold behavior observed in BEES studies on metal/oxide samples is amenable to a physical model comprising of STM photocurrent and a metal/oxide interface barrier. (C) 2012 American Vacuum Society. [DOI: 10.1116/1.3675606]