ZrB2-based Ohmic contacts to p-GaN

The annealing temperature dependence of contact resistance and layer stability of ZrB2/Ti/Au and Ni/Au/ZrB2/Ti/Au Ohmic contacts on p-GaN is reported. The as-deposited contacts are rectifying and transition to Ohmic behavior for annealing at 750 8C, a significant improvement in thermal stability compared to the conventional Ni/Au Ohmic contact on p-GaN, which is stable only to <600 8C. A minimum specific contact resistance of 2 10 3 V cm 2 was obtained for the ZrB2/Ti/Au after annealing at 800 8C while for Ni/Au/ZrB2/Ti/Au the minimum value was 10 4 V cm 2 at 900 8C. Auger Electron Spectroscopy profiling showed significant Ti, Ni and Zr out diffusion at 750 8C in the Ni/Au/ZrB2/Ti/Au while the Ti and Zr intermix at 900 8C in the ZrB2/Ti/Au. These boride-based contacts show promise for contacts to p-GaN in high temperature applications.