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

Abstract

We report the improved performance of InGaN/GaN-based light-emitting 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 x 10(-5) Omega cm(2) and reflectance of similar to 83% at a wavelength of 440 nm when annealed at 500 degrees C, which are much better than those of Ag only contacts. Blue LEDs fabricated with the 500 degrees C-annealed Ag/Zn/Ag reflectors show a forward voltage of 2.98 V at an injection current of 20 mA, which is lower than that (3.02 V) of LEDs with the annealed Ag only contacts. LEDs with the 500 degrees C-annealed Ag/Zn/Ag contacts exhibit 34% higher output power (at 20 mA) than LEDs with the annealed Ag only contacts. (C) 2012 Optical Society of America