Ohmic contacts on p-type GaN utilizing Pd/Ir/Au metallization were fabricated and characterized. Metallized samples that were rapid thermally annealed at 400 degrees C for 1 min exhibited linear current-voltage characteristics. Specific ohmic contact resistivities as low as 2 X 10(-5) Omega cm(2) were achieved. Auger electron spectroscopy and x-ray photoelectron spectroscopy depth profiles of annealed Pd/lr/Au contact revealed the formation. of Pd- and Ir-related alloys at the metalsemiconductor junction with the creation of Ga vacancies below the contact. The excellent contact resistance obtained is attributed to the formation of these Ga vacancies which resulted in the reduction of the depletion region width at the junction. (c) 2005 American Vacuum Society.