Low resistance and highly reflective Cu-Ni solid solution/Ag ohmic contacts to p-GaN for flip-chip light emitting diodes

We have investigated highly low resistance and reflective Cu-Ni solid solution/Ag ohmic contacts to p-GaN for flip-chip light emitting diodes (LEDs) for solid-state lighting applications. The Cu-Ni solid solution/Ag contacts produce specific contact resistances in the range of 10^-5 - 10 ^-6 Ω cm² when annealed at temperatures of 450 and 550°C for 1 min in air ambient. Measurements show that the reflectance of the annealed Cu-Ni solid solution/Ag contacts is 82.6% at a wavelength of 460 nm. Blue LEDs are fabricated with the annealed Cu-Ni solid solution/Ag contacts and single Ag contacts. The typical I-V characteristic of the LEDs made with the annealed Cu-Ni solid solution/Ag contact layer gives a forward-bias voltage of 3.08 V at 20 mA.