Aluminum indium gallium nitride (AlInGaN) metal-insulator-semiconductor (MIS) ultraviolet-C (UV-C) photodetectors (PDs) with a Ni/Ir/Au multilayer contact were proposed and fabricated. The inserting layer of the high work function metal (Ir) can significantly reduce the dark current of PDs and enhance the device performance, which can be attributed to the formation of IrO2 in multilayer contact. With a 3.5 V reverse bias, it was found that the dark current densities of PDs with a Ni/Au conventional contact and a Ni/Ir/Au multilayer contact were 3.7 x 10(-8) A/cm(2) and 8.3 x 10(-9) A/cm(2), respectively. Although the responsivities of these two different PDs are almost the same, the rejection ratio of AlInGaN MIS PD with a Ni/Ir/Au contact was larger than that of PD with a Ni/Au contact. (C) 2009 Elsevier Ltd. All rights reserved.