Improved electrical and thermal properties of Ag contacts for GaN-based flip-chip light-emitting diodes by using a NiZn alloy capping layer

We investigate the effect of a 100 nm-thick NiZn alloy (10 wt% Zn) capping layer on the thermal and electrical properties of Ag reflectors (200 nm) for flip-chip light-emitting diodes (LEDs). It is shown that the introduction of the NiZn capping layer minimizes the formation of interfacial voids and surface agglomeration. Furthermore, LEDs fabricated with the NiZn-capping-layer-combined contacts produce better output power as compared to those with the Ag only reflectors. For example, the LEDs with the 400 ^{{ring operator}}C-annealed Ag/NiZn contacts give higher output power by ∼36% than those with the 400 ^{{ring operator}}C-annealed Ag only contacts. X-ray photoemission spectroscopy and Auger electron spectroscopy measurements are performed to understand the improved electrical properties of the LEDs fabricated with the NiZn-capping-layer-combined Ag contacts.