Iridium-containing and Ni(4 nm)/Au(6 nm) films were evaporated separately on the n(+)-InGaN-GaN short-period-superlattice (SPS) structure of light-emitting diodes (LEDs). The collective deposition of iridium and other metals as an ohmic contact induces the formation of highly transparent IrO2, which helps to enhance the light output and decrease the series resistance of LEDs. By comparing different metal films used as current spreading contact layer, lr/Ni film annealed at 500 degrees C for 20 min in O-2 ambient renders devices with lowest turn-on voltage at 20 mA and highest luminous intensity. Moreover, we also analyzed films using atomic force microscopy (AFM) with an emphasis on studying how the surface quality of Ir/Ni and Ni/Au films influences the current spreading and luminosity of LEDs. (c) 2006 Elsevier Ltd. All rights reserved.