The improvement of electrical properties of Pd-based contact to p-GaN by surface treatment

The surface treatment effect on the interfacial reaction and electrical pro perty of Au/Pd contacts to p-GaN has been investigated. The contact resista nce of Au/Pd contacts on boiling aqua regia treated p-GaN was lower than aq ua regia treated p-GaN by one order of magnitude. The specific contact resi stivity of Au/Pd contacts on boiling aqua regia treated p-GaN increased wit h annealing temperature, but that on aqua regia treated p-GaN decreased wit h annealing temperature and it showed minimum value after annealing at 700 degreesC. According to the results of the interfacial reaction, the Au/Pd c ontact metals reacted more easily with aqua regia treated p-GaN than boilin g aqua regia treated p-GaN. Xray photoelectron spectroscopy analysis reveal ed that the relative surface Ga-to-N ratio of boiling aqua regia treated p- GaN was lower than that of aqua regia treated p-GaN and the surface of p-Ga N was modified from Ga-termination to N-termination by surface treatment us ing boiling aqua regia. According to the results of surface analysis and in terfacial reaction of Au/Pd/p-GaN, it could be concluded that the different temperature dependence of contact resistance according to the surface trea tment conditions was related strongly to the surface modification of p-GaN from Ga-termination to N-termination.