LAUSR

Stable ohmic contacts are critical to enable efficient operation of high-voltage electronic devices using ultra-wide-bandgap semiconductors. Here we perform, for the first time, thermally-accelerated aging of Ti/Au ohmic interfaces to (010) β-Ga2O3. We find that a heavily doped semiconductor, doped n-type by Si-ion implantation, treated with reactive ion etch (RIE), results in a low specific contact resistance of ~10-5 Ω·cm2 that is stable upon accelerated thermal aging at 300 °C for 108 hours. The low resistance interface is due to thermionic-field emission of electrons over an inhomogeneous barrier. Scanning/transmission electron microscopy indicates that the multi-layered structure and elemental distribution across the contact interface, formed during a 1-min 470 °C post-metallization anneal, do not change noticeably over the aging period. A ~1 nm interfacial layer is observed by high-resolution microscopy at the Ti-TiOx/Ga2O3 interface on all samples exposed to RIE, which may contribute to their excellent stability. In addition, longer-range facet-like interfacial features are observed, which may contribute to the inhomogeneous barrier. In contrast, Ti/Au junctions to moderately-doped (010) Ga2O3 made with no RIE treatment exhibit a high contact resistance that increases upon accelerated aging, along with a partially-latticed matched interface. The methods used here to understand the process, structure, and electrical property relationships for Ti/Au contact interfaces to β-Ga2O3 can be applied to assess and tune the stability of a variety of other oxide semiconductor interfaces.