Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes

We have investigated Cu-doped In₂O₃(CIO)(3 nm)/ Ag(250 nm) schemes for forming high-quality ohmic contacts top-type GaN for high-power flip-chip light-emitting diodes (FCLEDs). It is shown that the CIO/ Ag contacts produce specific contact resistance of 1.28 × 10^-5 ω cm² and reflectance of about 90% at a wavelength of 460 nm when annealed at 530 °C for 1 min in air ambient. It is also shown that unlike single Ag contacts, the CIO/Ag contacts are fairly stable without surface and interface degradation although annealed at 530 °C for 1 min in air ambient. In addition, blue multiquantum-well InGaN/GaN LEDs fabricated with the annealed CIO/Ag contact layers give forward-bias voltages of around 3.0 V at an injection current of 20 mA. The results strongly indicate that the CIO/Ag scheme can be a highly promising p-type contact for high-power GaN-based FCLEDs for solid-state lighting application.