The role of nanosize Au dots in the contact characteristic of Au/Ni/NiO stacked films to p-type GaN is studied. The nanosize Au dots were fabricated by heating a 1-nm-thick Au film at 150 degrees C in nitrogen ambient for 6 min. The NiO(2 nm), Ni(2 nm), and Au(2 nm) films were deposited sequentially on p-GaN, without or with the preformed Au dots. Without the nanosize Au dots, the Au/Ni/NiO/p-GaN structure shows nonlinear current-voltage (I-V) curves, even after annealing at 400 degrees C. On the contrary, the Au/Ni/NiO/dot-Au/p-GaN structure exhibits linear I-V curves of ohmic behavior after annealing at 400 degrees C in oxygen ambient. The nanosize Au dots indirect contact with p-GaN imitate the microstructure of Au islands in the annealed Au-Ni system and they create a microstructure of the Au-NiO-GaN triple-phase junction. The mechanism for the formation of contact via annealing and the presence of triple-phase junction are discussed. (c) 2005 American Vacuum Society.