Annealing temperature dependence of contact resistance and stablity for Ti/Al/Pt/Au ohmic contacts to bulk n-ZnO

E-beam deposited Ti/Al/Pt/Au contacts on undoped (nsimilar to10(17) cm(-3)) bulk ZnO showed minimum. specific contact resistance, rho(c), of similar to6x10(-4) Omega cm(2) after annealing at 250degreesC. This value was essentially independent of the surface cleaning procedure employed, including sequential solvent cleaning or H-2 plasma exposure. Higher annealing temperatures degraded the rho(c), and Auger electron spectroscopy depth profiling revealed increasing intermixing of the metal layers. The Al outdiffuses to the surface at temperatures as low as 350 degreesC, and the contact metallization is almost completely intermixed by 600 degreesC. (C) 2003 American Vacuum Society.