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

We have investigated Cu-doped In2O3(CIO)(3nm)∕Ag(250nm) schemes for forming high-quality ohmic contacts to p-type GaN for high-power flip-chip light-emitting diodes (FCLEDs). It is shown that the CIO∕Ag contacts produce specific contact resistance of 1.28×10−5Ωcm2 and reflectance of about 90% at a wavelength of 460nm when annealed at 530°C for 1min 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 1min 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 3.0V at an injection current of 20mA. 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.