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Presence of nanosize Au dots on the formation of ohmic contact for the Ni–Au base film to p-GaN

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3 Author(s)
Yang, Jiin-Long ; Department of Materials Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan ; Chen, J.S. ; Chang, S.J.

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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 °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 °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 °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.

Published in:

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures  (Volume:23 ,  Issue: 5 )