Fabrication of a TiNx/Ni/Au contact on ZnO films with high thermal stability and low resistance

Abstract

A novel contact structure comprising of TiN1.22/Ni/Au has been deposited on Ga-doped and In-doped zinc oxide (ZnO) epilayer grown on a yttria-stabilized ZrO2 substrate. It is found that the contact resistivity ρc is around 10-7 Ω2 for heavily doped ZnO, whereas a ρc value of 10-5 Ω cm2 is achieved for ZnO with light doping concentration. Attributed to the barrier effect of TiN1.22 intermediate layers, thermal annealing does not change the contact resistivity, but it is affected significantly by different surface treatments (atomic oxygen or nitrogen). For atomic oxygen-treated ZnO surface, the carrier density is increased, which leads to lower contact resistivity. It is shown that the contact structure of TiN1.22/Ni/Au with TiN1.22 as the intermediate layer can provide a high-quality ohmic contact with low ρc and good thermal stability. © 2011 IEEE.