Annealing Stability of NiO/Ga2O3 Vertical Heterojunction Rectifiers

The stability of vertical geometry NiO/Ga2O3 rectifiers during two types of annealing were examined, namely (1) the annealing of NiO only, prior to the deposition of the Ni/Au metal anode stack, and (2) the annealing of the completed device. The devices were annealed in oxygen for 1 min at a temperature of up to 500 °C. The results show that annealing at 300 °C can lead to the best performance for both types of devices in terms of maximizing the breakdown voltage and on–off ratio, lowering the forward turn-on voltage, reducing the reverse leakage current, and maintaining the on resistance. The surface morphology remains smooth for 300 °C anneals, and the NiO exhibits a bandgap of 3.84 eV with an almost unity Ni2O3/NiO composition.