For the bias-assisted activation of p-GaN at low temperature in air, we deposited various metal contacts consisting of thin Ni/Au and Ni/Pt, and thick Ni layer structures. Annealing these metal contacts with an electrical bias enhances the diffusion of residual hydrogen in the p-GaN towards the interface. The hydrogen was enhanced accumulated at the interface between metal and p-GaN by bias applied. The extracted hydrogen can diffuse through the thin Ni/Au and Ni/Pt metal contacts and desorb from the surface under bias-assisted activation at 410°C in air. The total resistance of the metal contact to p-GaN after bias-assisted activation decreases without thermal damage. In contrast, for a thick Ni contact on p-GaN, hydrogen accumulated at the interface, and diffusion of hydrogen into the air was obstructed. This condition results in a deteriorated contact resistance and decreases the transport current of the metal contact to p-GaN. The bias-assisted activation with thin Ni/Pt or Ni/Au contacts at 410°C is practical to remove residual hydrogen from p-GaN and subsequently decreases the contact resistance.
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