(NH4)(2)S-x surface treatment was found to increase the barrier height (phi(Bn)) for Au/In0.53Ga0.47As Schottky junctions from 0.26 eV to 0.58 eV at 300 K as determined from Richardson plots. The ideality factor n thus decreased from 2.7 to 1.6 and the reverse saturation current density J(o) from 9.4 A cm(-2) to 3.4 x 10(-5) A cm(-2). The values of the effective Richardson constant were also evaluated. The chemical state of In0.53Ga0.47As surfaces before and after (NH4)(2)S-x modification, examined by X-ray photoelectron spectroscopy (XPS), indicated bond formation of S with In, Ga and As.