Ohmic contact properties and annealing effect for Au/Ni on p-Type P-Doped ZnO

Abstract

Au/Ni ohmic contact to p-type P-doped ZnO (P:ZnO) is succeeded and investigated. The specific contact resistance ρ c decreases with increasing annealing temperature up to 300°C, but increases beyond that. After annealing at 300°C, ρpc is 0.0052 cm2, a decrease by about 15 times from 0.076 cm2 of the as-deposited contact. The sheet resistance Rs of p-type P:ZnO monotonously increases with the annealing temperature. The mechanisms causing the ρ c and Rs variation with the annealing temperature are studied. During thermal annealing in vacuum (2× 10-5 mbar), competitions exist between Zn out-diffusion and Ni and Au diffusion into ZnO. Zn out-diffusion can improve the ohmic contact performance by producing more acceptors or surface states in the interfacial layer, while Ni and Au diffusion into ZnO can kill the acceptors or surface states in the interfacial layer. © 2009 The Electrochemical Society.