Article Vacancy-type defects introduced by mechanical polishing in ammonothermal GaN studied by a monoenergetic positron beam

Akira Uedono ORCID ; Shoji Ishibashi ORCID ; Kohei Shima ORCID ; Shigefusa F. Chichibu ; Kacper Sierakowski ORCID ; Makoto Oishi ORCID ; Noriyuki Okada ORCID ; Takuro Nagai SAMURAI ORCID ; Michal Bockowski ORCID

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Akira Uedono, Shoji Ishibashi, Kohei Shima, Shigefusa F. Chichibu, Kacper Sierakowski, Makoto Oishi, Noriyuki Okada, Takuro Nagai, Michal Bockowski. Vacancy-type defects introduced by mechanical polishing in ammonothermal GaN studied by a monoenergetic positron beam. Journal of Crystal Growth. 2026, 688 (), 128622. https://doi.org/10.1016/j.jcrysgro.2026.128622

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(abstract)

Vacancy-type defects introduced by mechanical polishing in basic ammonothermal GaN and their annealing behavior were studied using a monoenergetic positron beam. The major vacancy-type defect in the sample was identified as a Ga-vacancy (VGa) coupled with hydrogen atoms. After mechanical polishing, high-density dislocations and stacking faults were introduced in the subsurface region (< 240 nm). In this region, the vacancy-type defects detected by positron annihilation were divacancies (VGaVN) and their complexes with hydrogen atoms. After ultra-high-pressure annealing at 1400ºC, {0001} basal slip bands were the predominant defects observed using a transmission electron microscope. The major vacancy-type defects for the annealed samples were identified as VGa coupled with multiple VN [ex VGa(VN)3] and their complexes with hydrogen atoms. The observed annealing behavior of vacancies agreed with that estimated using photoluminescence spectroscopy.

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Keyword: Mechanical polishing, GaN, Vacancy, Defect, Positron annihilation

Date published: 2026-04-12

Publisher: Elsevier BV

Journal:

  • Journal of Crystal Growth (ISSN: 00220248) vol. 688 128622

Funding:

  • Government of Japan Ministry of Education Culture Sports Science and Technology JPMXP1223NM0137
  • Horizon Europe 101183211

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.6258

First published URL: https://doi.org/10.1016/j.jcrysgro.2026.128622

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Updated at: 2026-04-20 08:56:29 +0900

Published on MDR: 2026-04-20 10:25:48 +0900

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