Low-resistivity Au∕Ni Ohmic contacts to Sb-doped p-type ZnO

Abstract

Au ∕ Ni contacts were fabricated on Sb-doped p-type ZnO film, which was grown on n-type Si (100) substrate with a thin undoped ZnO buffer layer by molecular beam epitaxy. As-deposited contacts were rectifying while Ohmic behavior was achieved after thermally annealing the contacts in nitrogen environment. Contact resistance was determined by linear transmission line method and it decreased with the increase of annealing temperature. Low specific contact resistivity of 3.0×10−4Ωcm2 was obtained for sample annealed at 800°C for 60s. Secondary ion mass spectroscopy was used to analyze elemental profiles of the contacts before and after annealing. Zn vacancies created by outdiffusion of Zn are believed to couple with activated Sb atoms to increase the surface hole concentration enabling Ohmic contact formation.