InGaN Visible Photodiodes With Improved Performance Using Oxidized Ir Schottky Contact

Oxidized iridium (Ir) was employed as the Schottky contact of In_0.18Ga_0.82N photodiodes. The Schottky barrier height (SBH) increases from 0.70 eV for the as-deposited Ir contacts to 0.91 eV for the contacts annealed at 500 ° C in O₂ ambient, while the dark current at -3 V bias decreases from 4.65×10^-5 to 2.29×10^-9 A. A zero-bias responsivity of 32 mA/W was obtained at 410 nm in the devices with the oxidized contacts, corresponding to an external quantum efficiency of 10%. Analysis results indicate that the increased SBH and decreased leakage current can be mainly ascribed to two factors: 1) the higher work function of the IrO₂ contacts formed by oxidation annealing and 2) the reduction in the background electron concentration near the IrO₂/In_0.18Ga_0.82N interface caused by the generation of compensating group-III vacancies during the oxidation process. Besides, the oxidation of group-III elements may also play a minor role in the performance improvement.