The annealing temperature dependence of rectifying contact characteristics on epilayers of n-GaN using a ZrB2/Ti/Au metallization scheme deposited by sputtering are reported. A maximum barrier height of 0.57 eV was achieved on samples annealed at 200 degrees C, with the reverse breakdown voltage of the diodes also a maximum after this anneal. The barrier height was essentially independent of annealing temperature up to 700 degrees C even though Auger electron spectroscopy depth profiling showed the onset of inter-contact metallurgical reactions at 500 degrees C. The Ti began to outdiffuse to the surface at temperatures of 350 degrees C, while the ZrB2/GaN interface showed no evidence of reaction even at 800 degrees C. The reverse current magnitude of diodes fabricated using the ZrB2 contacts was larger than predicted by thermionic emission alone. (c) 2006 Elsevier B.V. All fights reserved.