High thermal stable and low resistance contacts to p-GaN for thin-GaN LED

In this work, we investigate the optical and electrical properties of inserting a Ni thin barrier between contact layer, NiO-Au, and reflective layer, Al after sequent elevated annealing in air ambient. The reflectivity of NiO-Au/Ni/Al p-GaN contact configurations is 61% in 470nm which is 10% higher than NiO-Au/Al p-GaN contact configurations, after 500°C annealing. By inserting a Ni barrier layer, the specific contact resistance of the NiO-Au/Ni/Al was maintained on the order of 10^-2 Ω-cm ², up to an annealing temperature of 500°C - The XPS results confirmed the function of the Ni barrier layer, and it shows relatively low atomic level of Al was detected in the GaN epi-layer. It was found that both the electrical and optical characteristics of NiO-Au/Ni/Al p-GaN contacts exhibited good thermal stability. This high thermal stable P-GaN enables the fabrication of thin-GaN LED device.