Improved Ni/SiC and ZrB$_{2}$/SiC Schottky Barrier Diodes by High Temperature Processing

High temperature processing was used to improve the barrier properties of SiC Schottky diodes fabricated with Ni and ZrB$_{2}$ Schottky contacts. The Ni/SiC diodes were annealed in vacuum at 500 $^{\circ}$C in 20-hour intervals for a total of 110 hours. The average Schottky barrier heights determined by I-V measurements, increased with annealing time from 1.48 eV for non-annealed contacts to 1.81 eV for those annealed for 20 hours. The improvement is believed to be due to the formation of nickel silicide. The ZrB$_{2}$ Schottky contacts for the ZrB$_{2}$/SiC diodes were deposited at temperatures between 20 $^{\circ}$C and 800 $^{\circ}$C. The barrier heights increased with the deposition temperature from an average value of 0.87 eV for contacts deposited at 20 $^{\circ}$C to 1.07 eV for those deposited at 600 $^{\circ}$C. The Rutherford backscattering spectra of the ZrB$_{2}$/SiC contacts revealed a decrease of oxygen with increase in the deposition temperature and showed no reaction at the ZrB$_{2}$/SiC interface. We ascribe the improvement of the ZrB$_{2}$/SiC diodes to the removal of oxygen from the contact when deposited at high temperatures.