Rare-earth metal Schottky-barrier contacts to GaAs

The electrical properties and interface chemistry of ideal (no interfacial oxide) rare-earth metal contacts to GaAs are investigated by using x-ray photoemission spectroscopy (XPS), current-voltage (I-V), and capacitance-voltage (C-V) techniques. The contacts were formed (in ultrahigh vacuum) by evaporation of Tb, Dy, and Er onto clean, n-type GaAs (100) surfaces. For each metal a substantial interface chemical reaction occurs in which GaAs is dissociated and a rare-earth arsenide is formed that results in a>12-Å-thick interface layer. The Schottky-barrier height, measured with I-V and C-V methods at the same interfaces characterized by XPS, for these rare-earth metals is 0.85 eV. By a comparison to selected other materials, the results for rare-earth metals emphasize that the Schottky-barrier height for ideal contacts to GaAs is independent of the contact work function, electronegativity, and interface chemical reactivity.