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PreprintCC BY 4.0arXiv

Halide donors in monoclinic- and corundum-phase Ga2O3 and Al2O3

  • Sai Mu
  • Haochen Wang
  • Yongjoong Shin
  • Zhi-Hao Wang
  • Chris G. Van de Walle
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Abstract

We present a systematic first-principles investigation of halide impurities (F and Cl) in Ga2O3 and Al2O3, considering both monoclinic and corundum phases. Our study of the structural properties, formation energies, and charge-state transition levels establishes the relative stability of different atomic configurations and charge states. We find that F and Cl on oxygen sites act as shallow donors in Ga2O3 in both the monoclinic and corundum phases. However, their behavior differs substantially as the band gap increases with greater Al compositions. Fluorine is prone to DX-center formation with increased Al composition, leading to self-compensation at 38% Al concentration in monoclinic (AlxGa1−x)2O3 and 70% Al concentration in corundum (AlxGa1−x)2O3. Chlorine is more resistant to DX-center formation: in monoclinic (AlxGa1−x)2O3, ClO on the lowest-energy oxygen site shows an onset of DX behavior at 50% alloy composition, while in corundum (AlxGa1−x)2O3 this onset for ClO occurs only at Al concentrations as high as 84%. We also study F and Cl interstitials, finding that they act as compensating centers but also exhibit migration barriers that are low enough for them to be removed by post-growth annealing. Surprisingly, in both monoclinic and corundum Al2O3, ClO exhibits a relatively shallow transition level located at ∼0.48 eV below the conduction-band minimum, much shallower than FO and other donor candidates. These remarkable results identify Cl as an unusually promising donor candidate in (AlxGa1−x)2O3 alloys and even pure Al2O3, although high formation energies and compensation will render observation of true n-type conductivity in Al2O3 difficult.

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Cite

BibTeXRIS
BibTeX
@misc{mu2026halide,
  title = {{Halide donors in monoclinic- and corundum-phase Ga$_2$O$_3$ and Al$_2$O$_3$}},
  author = {Sai Mu and Haochen Wang and Yongjoong Shin and Zhi-Hao Wang and Chris G. Van de Walle},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.30680},
  eprint = {2608.30680},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.30680},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Halide donors in monoclinic- and corundum-phase Ga_2O_3 and Al_2O_3
AU  - Sai Mu
AU  - Haochen Wang
AU  - Yongjoong Shin
AU  - Zhi-Hao Wang
AU  - Chris G. Van de Walle
PY  - 2026
DA  - 2026/08/31
PB  - arXiv
DO  - 10.48550/arxiv.2608.30680
UR  - https://arxiv.org/abs/2608.30680
AB  - We present a systematic first-principles investigation of halide impurities (F and Cl) in Ga_2O_3 and Al_2O_3, considering both monoclinic and corundum phases. Our study of the structural properties, formation energies, and charge-state transition levels establishes the relative stability of different atomic configurations and charge states. We find that F and Cl on oxygen sites act as shallow donors in Ga_2O_3 in both the monoclinic and corundum phases. However, their behavior differs substantially as the band gap increases with greater Al compositions. Fluorine is prone to DX-center formation with increased Al composition, leading to self-compensation at 38% Al concentration in monoclinic (Al_xGa_1−x)_2O_3 and 70% Al concentration in corundum (Al_xGa_1−x)_2O_3. Chlorine is more resistant to DX-center formation: in monoclinic (Al_xGa_1−x)_2O_3, Cl_O on the lowest-energy oxygen site shows an onset of DX behavior at 50% alloy composition, while in corundum (Al_xGa_1−x)_2O_3 this onset for Cl_O occurs only at Al concentrations as high as 84%. We also study F and Cl interstitials, finding that they act as compensating centers but also exhibit migration barriers that are low enough for them to be removed by post-growth annealing. Surprisingly, in both monoclinic and corundum Al_2O_3, Cl_O exhibits a relatively shallow transition level located at ∼0.48 eV below the conduction-band minimum, much shallower than F_O and other donor candidates. These remarkable results identify Cl as an unusually promising donor candidate in (Al_xGa_1−x)_2O_3 alloys and even pure Al_2O_3, although high formation energies and compensation will render observation of true n-type conductivity in Al_2O_3 difficult.
ER  -