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Process and characterization of ohmic contacts for beta-phase gallium oxide

  • Invited Feature Paper-Review
  • Focus Issue: Ultra-wide Bandgap Materials, Devices, and Systems
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Abstract

β-Ga2O3 is a promising material for next-generation power devices because of its ultra-wide bandgap, the commercial availability of bulk substrates, epitaxial growth, and ease of n-type doping. To fully exploit its potential, it is critical to establish fabrication processes to form low-resistance ohmic contacts with excellent long-term stability. Due to upward band bending and unavoidable redox reactions occurring at the contact interface, making a good ohmic contact to gallium oxide can be challenging. Herein, we use a process-structure-property approach to systematically review the reported processes for ohmic contact formation on gallium oxide, the contact microstructure, and the resulting electrical properties including charge transport physics. Furthermore, we describe the present evidence for ohmic contact stability under accelerated aging. Using thermodynamic assessment, we propose alternate ohmic contact materials candidates. Finally, we identify gaps in the scientific knowledge on ohmic contacts to Ga2O3 and highlight opportunities for future investigations.

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Adapted from Refs. [42, 43].

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Copyright 2020 American Chemical Society.

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Copyright 2020 American Chemical Society.

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Acknowledgments

This work was supported by the Department of the Navy, Office of Naval Research under ONR Award No. N00014-17-1-2998 with Dr. Paul Maki. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Office of Naval Research.

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  1. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA

    Ming-Hsun Lee & Rebecca L. Peterson

  2. Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109-2122, USA

    Rebecca L. Peterson

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Lee, MH., Peterson, R.L. Process and characterization of ohmic contacts for beta-phase gallium oxide. Journal of Materials Research 36, 4771–4789 (2021). https://doi.org/10.1557/s43578-021-00334-y

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