ZrB2 Schottky diode contacts on n-GaN

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 8C, 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 8C even though Auger electron spectroscopy depth profiling showed the onset of inter-contact metallurgical reactions at 500 8C. The Ti began to outdiffuse to the surface at temperatures of 350 8C, while the ZrB2/GaN interface showed no evidence of reaction even at 800 8C. The reverse current magnitude of diodes fabricated using the ZrB2 contacts was larger than predicted by thermionic emission alone.