Passivation of interface states in the Schottky barrier is an approach to enhance the properties of the Schottky devices. In this work, Au/0.8nm-GaN/n-GaAs Schottky structure is studied electrically in a wide temperature range. With increasing temperature, the reverse current Iinv increases from 1×10-7 A to 1×10-5 A, and the saturation current Is increases from 1×10-32 A to 5×10-7A. The series resistance Rs decreases with increasing temperature from 13.44 Ω to 4.25 Ω. The ideality factor n decreases from 10.64 to 1.15. The barrier height increases abnormally with increasing temperature from 0.54 eV at 80 K to 1.03 eV at 180 K, then decreases to 0.82 eV at 420 K. The abnormal behavior of and the high values of n in low temperature are due to the tunnel mechanisms effects, such as FE and TFE currents. FE mechanism is the dominant process at low temperatures (80-300 K) and TFE mechanism is the dominant one at high temperatures (300-420K). Finally, our structure presents an inhomogeneous barrier height, maybe caused by the thin GaN interface layer.