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Interfacial Reactions of Titanium/Gold Ohmic Contacts with Sn-doped Beta-Ga2O3

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University of Michigan Ann Arbor United States

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Here we investigated interfacial reactions and interdiffusion of titaniumgold ohmic contacts with a tin-doped single-crystal beta-Ga2O3 010 substrate. After annealing at 470 deg C for 1 min in N2 to form an ohmic contact, we studied the interface via scanning transmission electron microscopy and transmission electron microscopy with energy dispersive X-ray spectroscopy as well as electron energy loss spectroscopy. At the interface, annealing causes Ti to diffuse and oxidize, reducing Ga2O3 at the interface. This forms a defective beta-Ga2O3 layer of 3-5 nm that has a relatively high Ti concentration. Above this is a 3-5 nm layer of Ti-TiOx that is partially lattice matched to the beta-Ga2O3 substrate. The thermodynamic favorability of these redox reactions was explained by calculating Gibbs free energies of the reactions. In addition, the anneal causes interdiffusion of Ti and Au, until Au is in contact with the thin Ti-TiOx layer. A layer of Ti-rich nanocrystals, around 5 nm in diameter, is formed within the Au-Ti intermixed matrix, about 3 nm above the Ti-TiOx layer. Based on these observations, the ohmic properties are tentatively attributed to the interdiffusion of Ti and Au and the resulting thin Ti-TiOx layer, which helps band alignment. In addition, lattice matching of the defective Ga2O3 and Ti-TiOx layers to beta-Ga2O3 facilitates the transport of carriers. A physical understanding of TiAu metallization can provide insights into future materials selection for thermally stable contacts in beta-Ga2O3 power devices.

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Journal Article - Open Access

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APL Materials , 7, 01 Jan 0001, 01 Jan 0001, All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (



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Approved For Public Release;

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