Oxidation Treatment On Ni/Au Ohmic Contacts To P-Type Gan

Current-voltage (I-V) characteristics, transmission line method (TLM), and optical transmittance measurements are performed to investigate the effects of thermal oxidation and plasma-induced oxidation treatments on Ni/Au contacts to p-type GaN. Whether oxidation and thermal annealing are performed simultaneously or in succession, the specific contact resistances of Au/Ni/p-GaN are reduced. As to plasma-induced oxidation, neither no-oxidation nor long-time oxidation treatments on Ni/Au layers are suitable for obtaining a low-resistance Ohmic contact. The roles of oxidation are believed to activate the Mg acceptor in p-GaN and to form an oxygenous intermediate semi-conductor layer, which may lower the Schottky barrier height between the metal layer and p-GaN. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.