NiGa₂O₄ interfacial layers in NiO/Ga₂O₃ heterojunction diodes at high temperature

NiO/Ga2O3 heterojunction diodes have attracted attention for high-power applications, but their high temperature performance and reliability remain underexplored. Here, we report the time evolution of the electrical properties in the widely studied p-NiO/n-Ga2O3 heterojunction diodes and formation of NiGa2O4 interfacial layers at high temperatures. Results of our thermal cycling experiment show an initial leakage current increase which stabilizes after sustained thermal load, due to reactions at the NiO-Ga2O3 interface. High-resolution TEM microstructure analysis of the devices after thermal cycling indicates that the NiO-Ga2O3 interface forms a ternary compound at high temperatures, and thermodynamic calculations suggest the formation of the spinel NiGa2O4 layer between NiO and Ga2O3. First-principles defect calculations find that NiGa2O4 shows low p-type intrinsic doping and hence can serve to limit electric field crowding at the interface. Vertical NiO/Ga2O3 diodes with intentionally grown similar to 5 nm thin spinel-type NiGa2O4 interfacial layers show an excellent device ON/OFF ratio of >1010 ( +/- 3 V), VON of similar to 1.9 V, and increased breakdown voltage of similar to 1.2 kV for an initial unoptimized 300 mu m diameter device. These p-n heterojunction diodes are promising for high-voltage, high temperature applications. (C) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).