High-temperature gold metallization for ZnO nanowire device on a SiC substrate

Gold is commonly used nowadays in metal contacts to nanowire devices. Due to their small size, nanowire devices often get heat up enough to cause a reaction of the contact and substrate, whether during operation or as a result of a spontaneous pulse of an electrostatic discharge. In most cases, the point of failure is the metallization, as is the case studied here. Gold is useful not only for its good electrical conductance but also because it is a good heat conductor and inert to the ambient. To improve the survivability of a gold metallization for nanowire devices incorporating ZnO nanowire atop a SiC substrate, we used a sputter-deposited Ti-Si-N ternary diffusion barrier layer and a Ti adhesion layer between the top gold layer and a 4H-SiC substrate that survives 30 min of vacuum annealing at 850°C and 5 days of annealing at 500° C in Ar. Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy were used to test the integrity of the layers before and after annealing both with and without the diffusion barrier. Current-voltage characteristics were measured up to 75 V in air to test the metallization.