BALLISTIC ELECTRON-EMISSION SPECTROSCOPY OF METALS ON GAP(110)

Ballistic electron emission spectroscopy (BEES), a technique based on the scanning tunneling microscope (STM), was used to measure Schottky barrier heights of metals on cleaved n-type GaP(110). The threshold voltages V0 for current detection in the semiconductor were found to be uniform to within +/- 0.02 V over the sample surface for any given metal on GaP. A transport model for the current I(c) crossing the barrier, that includes both nonclassical transmission across the metal-semiconductor interface and electron scattering in the metal, yields I(c) proportional-to (V - V0)5/2 near threshold. The value of V0 extracted from the data, which represents the Schottky barrier height, depends somewhat on the details of the transport model. Our best estimates of the Schottky barrier heights, within +/- 0.03 eV, are 1.07 (Mg), 1.11 (Ni), 1.14 (Bi), 1.25 (Cu), 1.31 (Ag), and 1.46 eV (Au).