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We previously reported a powerful method to improve dielectric/GaN interface properties: the dummy SiO2 process [Y. Irokawa et al., ECS J. Solid State Sci. Technol. 13, 085003 (2024)]. Here, GaN metal-oxide-semiconductor (MOS) interfaces prepared with this process were investigated using a sub-bandgap photo-assisted capacitance–voltage technique. GaN MOS interfaces were previously revealed to have deep states, and the dummy process was expected to reduce the number of deep states through its interface modification process. However, the deep state densities in Al2O3/GaN MOS interfaces after the dummy process did not substantially change compared with those in devices fabricated without the dummy process. Meanwhile, we recently observed oxygen atoms in positions proximate to nitrogen sites in MOS interface regions, with the GaN crystal maintaining the same structure [J. Uzuhashi et al. ECS J. Solid State Sci. Technol. 14, 085001 (2025)]. We therefore performed first-principles calculations and found that, under certain circumstances, a pair of oxygen atoms replacing nitrogen atoms in GaN created deep states in the bandgap, with slight displacements, similar to DX centers; this substitution could be one of the origins of deep states in GaN MOS interfaces.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: GaN

Date published: 2026-05-01

Publisher: The Electrochemical Society

Journal:

• ECS Journal of Solid State Science and Technology (ISSN: 21628769) vol. 15 issue. 5 055002

Funding:

• Ministry of Education, Culture, Sports, Science and Technology, Japan JPJ009777
• JSPS KAKENHI 23K03949

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

MDR DOI:

First published URL: https://doi.org/10.1149/2162-8777/ae6689

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Updated at: 2026-05-13 10:14:20 +0900

Published on MDR: 2026-05-13 12:28:43 +0900