Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

Ballistic electron emission spectroscopy of metals on GaP(110)

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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<inf>0</inf> 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<inf>c</inf> crossing the barrier, that includes both nonclassical transmission across the metal-semiconductor interface and electron scattering in the metal, yields I<inf>c</inf> ∝ (V -V<inf>0</inf>)<sup>5/2</sup> near threshold. The value of V<inf>0</inf> 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).