Abstract
In this study, all the samples AgPt(6 at%), AgPt(4 at%), AgPt(2 at%), Pt(2 nm)/Ag(150 nm), AgRh(2 at%) and AgRu(2 at%) were deposited on the p-GaN by dual E-gun evaporation system. The samples were annealed at 500℃ by two different annealing conditions, furnace annealing(FA) in air ambient for 10 min, and rapid thermal annealing(RTA) in air ambient for 1 min. Thermal stability test were performed by annealing at 400℃in air ambient for 60 min. Optoelectricproperties and thermal stability of p-GaN/AgPt, p-GaN/AgRu and p-GaN/AgRh reflective ohmic contacts were investigated by SEM analysis, reflectance at 460 nm, sheet resistance of metal film, and specific contact resistance.The result show annealed AgPt(6 at%), AgPt(4 at%),AgRh(2 at%) and AgRu(2 at%) could suppress the agglomeration of Ag film.In AgPt(6 at%) and AgPt(4 at%),Ag would produce lateral diffusion causing electrode leakage phenomenon when aging at 400 ℃ for one hour. Comprehensive consideration above-mentioned properties,AgRu (2 at%) alloys thin films are excellent.After anneal 1min in air at 500 ℃, the AgRu(2 at%) reflectors produce low specific contact resistance(7.4 × 10-4 Ω-cm2), high reflectivity(93% at 460nm),good sheet resistance of the metal thin film(0.2 Ω/□), and good thermal stability. Otherwise, we could also find that the work function of the magnitude of the noble metal element itself could't be the main cause of the magnitude of the specific contact resistance,when small amount of Ag and a noble metal (Pt, Ru, Rh) alloy is formed.