Highly reliable Ag/Zn/Ag ohmic reflector for high-power GaN-based vertical light-emitting diode

We report the improved performance of InGaN/GaN-based lightemitting diodes (LEDs) through Ag reflectors combined with a Zn middle layer. It is shown that the Zn middle layer (5 nm thick) suppresses the agglomeration of Ag reflectors by forming ZnO and dissolving into Ag. The Ag/Zn/Ag contacts show a specific contact resistance of 6.2 × 10-5 cm2 and reflectance of ∼83% at a wavelength of 440 nm when annealed at 500 Cwhich are much better than those of Ag only contacts. Blue LEDs fabricated with the 500 C-annealed Ag/Zn/Ag reflectors show a forward voltage of 2.98 V at an injection current of 20 mAwhich is lower than that (3.02 V) of LEDs with the annealed Ag only contacts. LEDs with the 500 C-annealed Ag/Zn/Ag contacts exhibit 34% higher output power (at 20 mA) than LEDs with the annealed Ag only contacts.