InGaN/GaN light-emitting diodes with ITO p-contact layers prepared by RF sputtering

Indium tin oxide (250 nm) and Ni(5 nm)/Au(10 nm) films were successfully deposited onto both glass substrates and p-GaN epitaxial layers. The normalized transmittance of the as-deposited ITO film was 90.6% at 450 nm, which was much larger than that of Ni/Au film. The transmittance of the RF sputtered ITO film could be increased to 97.8% with in situ annealing. In situ annealing of ITO films would also improve the electrical properties of ITO on p-GaN. Nitride-based light-emitting diodes (LEDs) were also fabricated. It was found that the 20 mA forward voltage was 3.16 V, 5.74 V and 4.28 V for the LEDs with Ni/Au, as-deposited ITO and in situ annealed ITO p-contact layer, respectively.