Ultrathin stable Ohmic contacts for high-temperature operation of β-Ga2O3 devices

Beta gallium oxide (beta-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 degrees 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 degrees 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 degrees C in vacuum (<= 10(-4) Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550 degrees C in flowing N-2. 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. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Beta gallium oxide (beta-Ga2O3) shows great potential for high-temperature, high-power, and sensing electronics applications. However, stable metallization layers for Ohmic contacts at high temperatures have been a challenge. In this study, we demonstrate stable Ohmic contacts for Ga2O3 devices operating at temperatures up to 500-600 degrees C using ultrathin Ti layers with a self-limiting interfacial reaction.