Temperature-Agnostic Pt/Au Ohmic Contacts on n-Type Gallium Nitride for Self-Aligned MOSFETs

Reilly, Kevin James; Binder, Andrew T.; Steinfeldt, Jeffrey Allen; Allerman, Andrew A.; Kaplar, Robert J.

doi:10.1109/TMAT.2025.3559869

Temperature-Agnostic Pt/Au Ohmic Contacts on n-Type Gallium Nitride for Self-Aligned MOSFETs

Journal Article · Fri Apr 11 00:00:00 EDT 2025 · IEEE Transactions on Materials for Electron Devices

DOI:https://doi.org/10.1109/TMAT.2025.3559869· OSTI ID:2585660

^[1]; ^[1]; ^[1]; Allerman, Andrew A. ^[1]; ^[1]

Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

Five alternative metals are investigated as ohmic contacts to n-GaN including Cr/Au, Mo/Au, Pt/Au, Pd/Au, and Ge/Au. Ti-based contacts are traditionally used for ohmic contacts on n-GaN. However, conventional Ti/Al/Ni/Au metallization is found to be incompatible with a self-aligned process for GaN trench MOSFETs due to wet etch restrictions. Therefore, an alternative metallization is needed that is unreactive to the etch chemistry used in the self-aligned process. Additionally, the contact should remain ohmic following anneal at 900 °C so that contact formation can precede the anneal required for p-dopant activation. Here, in the present work, an n-GaN bilayer, consisting of a thin heavily doped contact layer (n₀ = 1 × 10²⁰ cm⁻³) atop a thick lesser doped layer, is used to demonstrate ohmic contacts of alternative metals with low specific contact resistance and extended thermal budget. Cr/Au ohmic contacts are demonstrated up to anneal temperatures of 800 °C, an increase of 200 °C compared to the highest known reports for Cr/Au contacts on n-GaN. Pt/Au metallization is demonstrated as an ohmic contact to n-GaN for the first time and exhibits true temperature-agnostic behavior up to anneal temperatures of 900 °C with specific contact resistance that is near parity with Ti/Al/Ni/Au. The temperature-agnostic behavior of Pt/Au ohmic contacts on the n-GaN bilayer, in addition to chemical compatibility with the self-aligned process, positions Pt/Au contacts as a key enabling element for self-aligned trench MOSFETs on GaN.

View Accepted Manuscript (DOE)

Research Organization:: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO)

Grant/Contract Number:: NA0003525

OSTI ID:: 2585660

Report Number(s):: SAND--2025-06450J; 1764007

Journal Information:: IEEE Transactions on Materials for Electron Devices, Journal Name: IEEE Transactions on Materials for Electron Devices Vol. 2; ISSN 2993-1576

Publisher:: Institute of Electrical and Electronics Engineers (IEEE)Copyright Statement

Country of Publication:: United States

Language:: English

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