Zn/Au ohmic contacts on n-type ZnO epitaxial layers for light-emitting devices

We have investigated thermally stable and low resistance Zn/ Au ohmic contacts on Al-doped n-type ZnO layers. The Zn/ Au contacts produce linear current-voltage behaviors when annealed at temperatures in the range of 300 to 600 degrees C for 1 min in a nitrogen ambient. The samples annealed at 500 degrees C yielded contact resistivity as low as 2.36 X 10(-5) Omega cm(2). However, annealing the samples at 600 degrees C degraded their electrical characteristics with contact resistivity of 1.01 X 10(-2) Omega cm(2). Based on the X-ray diffraction and X-ray photoemission spectroscopy results, the possible formation and degradation mechanisms of the Zn/ Au contacts are described and discussed. (c) 2005 The Electrochemical Society.