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 V 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 crossing the barrier, that includes both nonclassical transmission across the metal-semiconductor interface and electron scattering in the metal, yields I ∝ (V -V)^5/2 near threshold. The value of V 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).