High-Reflectance and Thermally Stable AgCu Alloy p-Type Reflectors for GaN-Based Light-Emitting Diodes

We report on the formation of high-quality AgCu alloy p-type reflectors for GaN-based light-emitting diodes (LEDs). Compared with Ag contacts, the AgCu alloy reflectors produce lower specific contact resistance (7.5times10^-5 Omegamiddotcm²), higher light reflectance (89.5% at 400 nm), and better thermal stability (absence of interfacial voids), when annealed at 400 degC in N₂ : O₂(=1:1) ambient. LEDs fabricated with the AgCu reflectors show light output power better than that of LEDs with the Ag reflectors. The ohmic mechanism for the AgCu alloy reflectors is explained in terms of the formation of Ag-Ga solid solution and the presence of Cu-oxide nano-particles at the contact/GaN interface