We investigated the passivation effects of hydrogen gas on the Au/n-GaAs Schottky barrier diodes in a wide temperature range. Reference diodes were prepared by evaporating barrier metal on semiconductor wafers un-annealed in N-2 gas atmosphere. The other diodes were made by evaporating barrier metal on n-GaAs semiconductor substrates annealed in H, atmosphere. Then, electrical measurements of all diodes were carried out by using closed-cycle Helium cryostat by steps of 20 K in the temperature range of 80-300 K in dark. The basic diode parameters such as ideality factor and barrier height were consequently extracted from electrical measurements. It was seen that ideality factors increased and barrier heights decreased with the decreasing temperature. The case was attributed to barrier inhomogeneity at the metal/semiconductor interface. Barrier heights of the diodes made from samples annealed in H, gas atmosphere were smaller than those of reference diodes at low temperatures. Here, it was ascribed to the fact that hydrogen atoms passivated dangling bonds on semiconductor surface in accordance with former studies. (c) 2007 Elsevier B. V. All rights reserved.