This work reports the electrical characteristics comparison study between ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ based heterojunction diodes (HJD) on halide vapor phase epitaxy (HVPE) grown β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ epitaxial layers. Both as-fabricated ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs exhibited forward current density in a range of 130–150 $\mathrm{A}/{\mathrm{cm}}^2$ at 5 V with rectifying ratios $>{10}^{10}$ and a reverse leakage current density at ${10}^{-8} \mathrm{A}/{\mathrm{cm}}^2$ at $-5\mathrm{V}$. The differential specific on-resistance of ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs was $12.01\mathrm{m}\mathrm{\Omega }{\mathrm{cm}}^2$ and $12.05\mathrm{m}\mathrm{\Omega }{\mathrm{cm}}^2$, respectively. Breakdown voltages of ${\mathrm{Cr}}_2{\mathrm{O}}_3$ HJDs ranged from 1.4–1.9 kV and 1.5–2.3 kV for ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs. Theoretical band alignment between ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ was calculated from first principles. The ambient exposed ${\mathrm{NiO}}_{\mathrm{x}}$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJDs’ forward current density degraded after 10 days while that of ${\mathrm{Cr}}_2{\mathrm{O}}_3$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJDs’ remained nearly unchanged after the same amount of time. It was later confirmed that the ambient exposed sputtered ${\mathrm{NiO}}_{\mathrm{x}}$ sheet resistance (${\mathrm{R}}_{\mathrm{sh}}$) degradation gave rise to the reduction of the forward current density of the ${\mathrm{NiO}}_{\mathrm{x}}$ based HJDs, and water (${\mathrm{H}}_2\mathrm{O}$) was qualitatively determined to be the agent attributed to the forward conduction degradation by measuring the ${\mathrm{R}}_{\mathrm{sh}}$ of ${\mathrm{NiO}}_{\mathrm{x}}$-on-sapphire reference wafer after exposing it to different environments. The ${\mathrm{Cr}}_2{\mathrm{O}}_3$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJD also exhibited enhanced thermal stability compared to the ${\mathrm{NiO}}_{\mathrm{x}}$/β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ heterostructures at elevated temperatures.

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• Capacitance
• Electrical conductivity
• Engineering
• Devices
• Diodes
• Charge