Formation and Effect of Thermal Annealing for Low-Resistance Ni/Au Ohmic Contact to Phosphorous-Doped p-Type ZnO

Abstract

We report on a Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the phosphorus-doped p-type ZnO with a hole concentration of cm−3. As-deposited Ni/Au contacts to p-type ZnO showed a specific contact resistance of Ω cm2 by forming Ni-Zn phase to increase the hole concentration near the ZnO surface. The specific contact resistance was decreased with increasing the thermal annealing temperature. When the Ni/Au contact was annealed at 600°C for 30 s in an air ambient, the specific contact resistance was greatly decreased to Ω cm2. The improved ohmic property was attributed to an increase in the hole concentration by the formation of Ni-Zn and Au-Zn phases due to the outdiffusion of Zn during the thermal annealing process. © 2005 The Electrochemical Society. All rights reserved.