Effect of thermal annealing for W/β-Ga₂O₃ Schottky diodes up to 600 °c

The electrical and structural properties of sputter-deposited W Schottky contacts with Au overlayers on n-type Ga₂O₃ are found to be basically stable up to 500 °C. The reverse leakage in diode structures increases markedly (factor of 2) for higher temperature annealing of 550-600 °C. The sputter deposition process introduces near-surface damage that reduces the Schottky barrier height in the as-deposited state (0.71 eV), but this increases to 0.81 eV after a 60 s anneal at 500 °C. This is significantly lower than conventional Ni/Au (1.07 eV), but W is much more thermally stable, as evidenced by Auger electron spectroscopy of the contact and interfacial region and the minimal change in contact morphology. The contacts are used to demonstrate 1.2 A switching of forward current to -300 V reverse bias with a reverse recovery time of 100 ns and a dI/dt value of 2.14 A/μs. The on/off current ratios were ≥10⁶ at -100 V reverse bias, and the power figure-of-merit was 14.4 MW cm^-2.