Zinc oxide (ZnO) is a strong candidate for replacing GaN semiconductors that are of great technological importance for the fabrication of optoelectronic devices

because of its unique electrical and optical properties

namely

its large bandgap of 3.37 eV

low power threshold for optical pumping at room temperature

and highly efficient UV emission resulting from a large exciton binding energy of 60 meV at room tempe-rature

and an easy wet etching process. For the realization of high performance ZnO-based optoelectronic devices

the achievement of high quality ohmic contacts is essential. So far

the metal schemes for ohmic contact to n-type zno mainly focus on Al base and Ti base

such as

Al

Al/Pt

Ti/Au

Ti/Al/Pt/Au

and nonalloyed In. Pt-Ga via rapid annealing process

low specific contact resistance scope from 10

-4

10

-8

Ω·cm

2

was obtained. For p-type ZnO

due to its difficulty in doping

contact to p-type ZnO has not been extensive studied.There’s only a few report on Ni/Au

Au

Au/Ni/Au and Ni/ITO contact to Sb doped

P doped and ZnMgO p-type ZnO. Replacing O site by N is considered as a effective route to realize p-type ZnO. In this paper

we studied rapid annealing effect on the electric character of the N-doped ZnO film and effect on Ni/Au contacts to the N-doped ZnO film.A conversion from rectifying to ohmic behavior is observed for Ni/Au contacts to N-doped ZnO film. The as-deposited Ni/Au contacts to the as grown ZnO film shows nonlinear rectifying behavior

linear ohmic behavior appeared after rapid annealing at temperature up to 350℃. A minimum specific contact resistance of 8×10

-4

Ω·cm

2

was obtained after annealing at 650℃. Higher annealing temperatures degrade the ohmic contact behavior. Hall measurement suggests that the conductive type changed from p-type to n-type via rapid annealing process

which corresponds partly to the changed contact behavior. Analyses of the elements depth profile by Auger electron spectroscopy and glancing angle X-ray diffraction identified the reaction product in the interface of the metal and ZnO. Results suggest the addition of surface state and interface state can lower the barrier height and increase the tunnel path

which also contribute much to the improvement of Ni/Au ohmic contacts to N-doped ZnO.