Article Infrared Near-Field Spectroscopy of AlGaN/GaN Heterostructures for Probing Two-Dimensional Electron Gas

Ilario Bisignano SAMURAI ORCID (National Institute for Materials Science) ; Masataka Imura SAMURAI ORCID (National Institute for Materials Science) ; Nicholaus Kevin Tanjaya SAMURAI ORCID (National Institute for Materials Science) ; Ming-Jyun Ye ; Noriyuki Okada (National Institute for Materials Science) ; Satoshi Ishii SAMURAI ORCID (National Institute for Materials Science)

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Ilario Bisignano, Masataka Imura, Nicholaus Kevin Tanjaya, Ming-Jyun Ye, Noriyuki Okada, Satoshi Ishii. Infrared Near-Field Spectroscopy of AlGaN/GaN Heterostructures for Probing Two-Dimensional Electron Gas. ACS Applied Materials & Interfaces. 2025, 17 (35), 50077-50084. https://doi.org/10.1021/acsami.5c12417

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(abstract)

Infrared near-field spectroscopy, or nano-FTIR, offers nanoscale resolution in three dimensions to probe the chemical and physical properties of samples, making it a unique characterization tool. This nanoscopic resolution in three-dimension is particularly suitable to probe two-dimensional electron gas (2DEG) where a 2DEG has an effective thickness of a few nanometers and exists a few tens of nanometers below the capping layer. This work employs nano-FTIR spectroscopy to non-invasively probe the 2DEG of AlGaN/GaN heterostructures which are crucial for high-power electronic devices and sensing applications. Higher harmonic amplitude and phase of the nano-FTIR spectra are sensitive enough to the carrier concentration of the 2DEGs, which is supported by the analytical calculations based on the finite dipole model. A comparative analysis confirms that incorporating the 2DEG layer into the model is essential to match spectral features with experimental observations. Furthermore, hyperspectral imaging of a cross-sectional sample provides a visual representation of the 2DEG. The findings demonstrate that nano-FTIR enables the characterization of 2DEG in AlGaN/GaN heterostructures with nanometric resolution in ambient conditions, hence expanding its applicability in the study of such systems.

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Keyword: Two-dimensional electron gas, AlGaN/GaN, Nano-FTIR, Infrared spectroscopy

Date published: 2025-09-03

Publisher: American Chemical Society (ACS)

Journal:

  • ACS Applied Materials & Interfaces (ISSN: 19448252) vol. 17 issue. 35 p. 50077-50084

Funding:

  • Japan Society for the Promotion of Science 22H01917
  • Japan Society for the Promotion of Science 24K21723
  • Fusion Oriented REsearch for disruptive Science and Technology JPMJFR2139

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1021/acsami.5c12417

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Updated at: 2025-11-10 12:30:06 +0900

Published on MDR: 2025-11-10 12:24:32 +0900

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