Improved light output of GaN-based light-emitting diodes by using AgNi reflective contacts

We investigated the light output power of blue light-emitting diodes (LEDs) fabricated with AgNi contacts as a function of the Ni content. Annealing the AgNi contacts at 400°C in air significantly improved their electrical characteristics. The AgNi samples with 10.0 wt.% Ni showed reflectance of 80.9% at 460 nm, whereas the Ag-only contacts gave 71.1%. After annealing at 400°C, the AgNi contacts exhibited better thermal stability than did the Ag-only contacts. Their current-voltage relationships showed that blue LEDs fabricated with Ag-only contacts gave a forward voltage of 3.33 V at 20 mA, whereas those fabricated with AgNi contacts with 10.0 wt.% Ni produced 3.03 V. LEDs fabricated with the AgNi contacts exhibited output power higher by 5.9% to 19.1% than those with Ag-only contacts. Based on scanning electron microscopy and x-ray photoemission spectroscopy results, the improved thermal and electrical behaviors are described and discussed.