Gallium oxide heterojunction diodes for 400 °C high-temperature applications

β-Ga${}_2$O${}_3$-based semiconductor devices are expected to have significantly improved high-power and high-temperature performance due to its ultrawide bandgap of close to 5 eV. However, the high-temperature operation of these ultrawide-bandgap devices is usually limited by the relatively low 1-2 eV built-in potential at the Schottky barrier with most high-work-function metals. Herein, heterojunction p-NiO/n-β-Ga${}_2$O${}_3$ diodes fabrication and optimization for high-temperature device applications are reported, demonstrating a current rectification ratio (I${}_{ON}$/I${}_{OFF}$) of more than 10${}^6$ at 410 °C. The NiO heterojunction diode can achieve higher turn-on (V${}_{ON}$) voltage and lower reverse leakage current compared to the Ni-based Schottky diode fabricated on the same single-crystal β-Ga${}_2$O${}_3$ substrate, despite charge transport dominated by interfacial recombination. Electrical characterization and device modeling show that these advantages are due to a higher built-in potential and additional band offset. These results suggest that heterojunction p-n diodes based on β-Ga${}_2$O${}_3$ can significantly improve high-temperature electronic device and sensor performance. (© 2023 Wiley‐VCH GmbH)