Stable Contact Development for High-Temperature β-Ga₂O₃ Device Operation

β-Ga₂O₃ shows promise in the high-temperature power electronics space for high-voltage and high-frequency switching applications. However, due to it being an oxide, metallization presents unique thermodynamic challenges. The most common ohmic contact designs have been repeatedly demonstrated to fail at even moderately elevated temperatures due to a combination of thermodynamically favorable interfacial reactions and kinetically favored diffusion processes. To address this issue, we purposefully leverage a self-limited interfacial reaction scheme by deploying an ohmic contact design (5nm Ti / 100nm Au) with an ultra-thin Ti layer that is designed to fully react, thereby eliminating thermodynamic instability and extraneous diffusion.

In addition to thermodynamic stability issues, many metallic Schottky contacts have shown difficulty maintaining high rectification ratios at useful voltage ranges due to the strong temperature dependence of reverse-bias carrier generation (i.e., thermionic and field emission). We explore the use of an oxidation step for various Schottky metals (e.g., Cr, Ni) to fabricate diodes that improve the high-temperature rectification stability of the diode while maintaining a reasonably low turn-on voltage.