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Beta gallium oxide (β-Ga2O3) shows significant promise in high-temperature, high-power, and sensing electronics applications. However, long-term stable metallization layers for Ohmic contacts at high temperatures present unique thermodynamic challenges. The current most common Ohmic contact design based on 20 nm of Ti has been repeatedly demonstrated to fail at even moderately elevated temperatures (300–400 °C) due to a combination of nonstoichiometric Ti/Ga2O3 interfacial reactions and kinetically favored Ti diffusion processes. Here, we demonstrate stable Ohmic contacts for Ga2O3 devices operating up to 500–600 °C using ultrathin Ti layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the 5 nm Ti/100 nm Au contact stack is designed to fully oxidize while forming an Ohmic contact, thereby limiting both thermodynamic and kinetic instability. This novel contact design strategy results in an epitaxial conductive anatase titanium oxide interface layer that enables low-resistance Ohmic contacts that are stable both under long-term continuous operation (>500 h) at 600 °C in vacuum (≤10−4 Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550 °C in flowing N2. This stable Ohmic contact design will accelerate the development of high-temperature devices by enabling research focus to shift toward rectifying interfaces and other interfacial layers. 

Abstract Ternary metal‐oxide material systems commonly crystallize in the perovskite crystal structure, which is utilized in numerous electronic applications. In contrast to oxides, there are no known nitride perovskites, likely due to the competition with oxidation, which makes the formation of pure nitride materials difficult and synthesis of oxynitride materials more common. While deposition of oxynitride perovskite thin films is important for many electronic applications, it is difficult to control oxygen and nitrogen stoichiometry. Lanthanum tungsten oxynitride (LaWN_3−δO_δ) thin films with varying La:W ratio are synthesized by combinatorial sputtering and characterized for their chemical composition, crystal structure, and microstructure. A three‐step synthesis method, which involves co‐sputtering, capping layer deposition, and rapid thermal annealing, is established for producing crystalline thin films while minimizing the oxygen content. Elemental depth profiling results show that the cation‐stoichiometric films contain approximately one oxygen for every five nitrogen (δ = 0.5). Synchrotron‐based diffraction indicates a tetragonal perovskite crystal structure. These results are discussed in terms of the perovskite tolerance factors, octahedral tilting, and bond valence. Overall, this synthesis and characterization is expected to pave the way toward future thin film property measurements of lanthanum tungsten oxynitrides and eventual synthesis of oxygen‐free nitride perovskites.