【Device Papers】Stability Study of >13.5 kV Field Plated NiO/β-Ga₂O₃ Heterojunction Rectifiers Fabricated on 4-Inch Wafers

      Researchers from Chemical Engineering, University of Florida have published a dissertation titled " Stability Study of >13.5 kV Field Plated NiO/β-Ga₂O₃ Heterojunction Rectifiers Fabricated on 4-Inch Wafers " in ECS Journal of Solid State Science and Technology.

Abstract

      100 μm diameter vertical NiO/β-Ga₂O₃ heterojunction diodes with dielectric-assisted field-plate edge termination were fabricated on a 4-inch β-Ga₂O₃ wafer with ∼10–14 μm thick Si-doped 8.5 × 1015 cm⁻³ drift layers demonstrating breakdown voltages (VB) exceeding 13.5 kV, limited by the measurement equipment, on-voltage (VON) of ∼2.2 V and on-state resistance RON of 5.5 mΩ×cm². The average critical breakdown field in heterojunctions was ∼9.6–13.5 MV/cm, within the reported theoretical value range from 8–15 MV/cm for β-Ga₂O₃. The associated maximum power figure-of-merit, VB2/RON of >33.1 GW/cm² was achieved. Scanning transmission electron microscopy (STEM) reveals a polycrystalline NiO layer with multiple crystallographic orientations and a well-defined device stack. Forward current–voltage measurements performed 10 days and 150 days after NiO deposition show stable turn-on behavior with only minor changes in low-bias current. Cross-sectional STEM and energy-dispersive X-ray spectroscopy (EDS) analysis indicate that the small degradation is associated with oxidation of the outer edge (~500 nm) of the Ni contact on NiO, while the NiO/β-Ga₂O₃ heterojunction remains intact. These results demonstrate stable ultra-high-voltage operation of NiO/β-Ga₂O₃ heterojunction rectifiers fabricated on wafer-scale substrates, highlighting their potential for next-generation extreme-voltage power electronics.

DOI：

https://doi.org/10.1149/2162-8777/ae72ce