The Schottky barrier height of Au deposited on (100) surfaces of n-type β-Ga2O3 single crystals was determined by current-voltage characteristics and high-resolution photoemission spectroscopy resulting in a common effective value of 1.04 ± 0.08 eV. Furthermore, the electron affinity of β-Ga2O3 and the work function of Au were determined to be 4.00 ± 0.05 eV and 5.23 ± 0.05 eV, respectively, yielding a barrier height of 1.23 eV according to the Schottky-Mott rule. The reduction of the Schottky-Mott barrier to the effective value was ascribed to the image-force effect and the action of metal-induced gap states, whereas extrinsic influences could be avoided.
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The barrier height determined from I-V is not very sensitive to the choice of the effective mass (or effective Richardson constant), since at room temperature, a change of that parameter by a factor of two will cause a change of only about 0.02 eV in the barrier height, Ref. 12.
With a net donor concentration of 1 × 1017 cm−3 comparable to that of our β-Ga2O3 crystals and a dielectric constant of about 10, one can roughly estimate a zero-bias image-force lowering of about 50 meV and an ideality factor between 1.01 and 1.02 (using formulas given in Ref. 7).
