Dramatic Improvement in the Rectifying Properties of Pd Schottky Contacts on β-Ga₂O₃ During Their High-Temperature Operation

β-Ga
₂
O
₃
is a candidate for high-efficiency power electronics and ultraviolet C (UVC) detectors capable of operating in harsh environments. However, electrical contacts that maintain their performance at high temperatures are likely to be important due to the material's low thermal conductivity. In this study, we report on a dramatic improvement in the rectifying performance of Pd Schottky contacts (SCs) on ( -201) and (010) β-Ga
₂
O
₃
at high temperatures in air. This effect involves a large thermally activated increase in the image-force-corrected barrier height ( Φ
_B,IF
) from 1.40 eV at room temperature (RT) to 1.75-2.20 eV, with most of the transition occurring between 250 °C and 450 °C. This improvement is due to the oxidation of the Pd SC layer that creates higher barrier height PdO regions that dominate the high-temperature current transport. In the most oxidized Pd SCs, Φ
_B,IF
increased to 2.20 eV at 500 °C with leakage currents of ~ 1×10
^-6
Acm
^-2
(-3 V) and rectification ratios (±3 V) of ~ 10
⁷
, at 500 °C, similar to the best results for diamond and SiC SCs. Interestingly, very good agreement between the temperature dependence of the built-in voltage of the thermally oxidized Pd SCs and the optical bandgap of β-Ga
₂
O
₃
(approximately -1.3 meV/°C in both cases) was observed between RT and 500 °C.