期刊
ACS NANO
卷 16, 期 8, 页码 11988-11997出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.2c01957
关键词
gallium oxide; Ti; Au ohmic contacts; charge transport; crystallographic anisotropy; microscopy characterization; contact resistance; interfacial reactions
类别
资金
- Department of the Navy, Office of Naval Research, under ONR [N00014-17-1-2998]
- Dr. Paul Maki [16ES1084K]
- Leibniz Association-Germany
- University of Michigan College of Engineering
- Novel Crystal Technology, Inc., and Advanced Electronics Group of Sojitz Machinery Corp.
In this study, the anisotropic nature of monoclinic Ga2O3 was utilized to improve Ti/Au ohmic contact performance. The findings suggest that the dominant charge transport mechanism across the Ti/Au-Ga2O3 junction depends on whether reactive ion etching was used prior to metallization.
Here we demonstrate a dramatic improvement in Ti/Au ohmic contact performance by utilizing the anisotropic nature of??-Ga2O3. Under a similar doping concentration, Ti/Au metallization on (100) Ga2O3 shows a specific contact resistivity 5.11 X 10???5 fl???cm2, while that on (010) Ga2O3 is as high as 3.29 X 10???3 fl???cm2. Temperature-dependent contact performance and analyses suggest that field emission or thermionic field emission is the dominant charge transport mechanism across the Ti/Au???(100) Ga2O3 junction, depending on whether reactive ion etching was used prior to metallization. Cross-sectional high-resolution microscopy and elemental mapping analysis show that the in situ-formed Ti-TiOx layer on (100) Ga2O3 is relatively thin (2???2.5 nm) and homogeneous, whereas that on (010) substrates is much thicker (3???5 nm) and shows nanoscale facet-like features at the interface. The anisotropic nature of monoclinic Ga2O3, including anisotropic surface energy and mass diffusivity, is likely to be the main cause of the differences observed under microscopy and in electrical properties. The findings here provide direct evidence and insights into the dependence of device performance on the atomic-scale structural anisotropy of ??-Ga2O3. Moreover, the investigative strategy here -combining comprehensive electrical and materials characterization of interfaces on different semiconductor orientations -can be applied to assess a variety of other anisotropic oxide junctions. Superscript/Subscript Available
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