Abstract
Gallium oxide is a promising ultra wide band gap semiconductor for applications in power electronics, photodetectors, and as a transparent host material or electrical conductor. Ion implantation is a technique used to tailor the properties of semiconductors. For further technological development of gallium oxide, it is therefore essential to understand how the material is affected by ion implantation. Crystalline materials typically lose their crystal structure after high-dose ion implantation, while gallium oxide instead transforms to a different crystal structure. In this thesis, we investigate the transformation, and show that initially monoclinic gallium oxide transforms to the defective spinel polymorph. The results reveal that the polymorph transformation is independent of the implanted species and is caused by the implantation-induced defect formation, rather than the chemistry of the implanted ions. Further, the transformation can be reversed through heat treatments. The work also reveals that germanium and silicon dioxide nanoparticles can be embedded in gallium oxide with ion implantation followed by annealing. The luminescence from implanted and annealed gallium oxide, including Cr-related luminescence, has been probed with high spatial resolution. These results advance the understanding of polymorph transformations from ion implantation and elucidate several important aspects of ion implantation in gallium oxide
List of papers
Paper I. S. B. Kjeldby, A. Azarov, P. D. Nguyen, V. Venkatachalapathy, R. Mikšová, A. Macková, A. Kuznetsov, Ø. Prytz and L. Vines, ”Radiation-induced defect accumulation and annealing in Si-implanted gallium oxide”, Journal of Applied Physics 131, 125701 (2022). DOI: 10.1063/5.0083858. The article is included in the thesis. Also available at: https://doi.org/10.1063/5.0083858 |
Paper II. J. García-Fernández, S. B. Kjeldby, P. D. Nguyen, O. B. Karlsen, L. Vines and Ø. Prytz, ”Formation of γ-Ga2O3 by ion implantation: Polymorphic phase transformation of β-Ga2O3”, Applied Physics Letters 121, 191601 (2022). DOI: 10.1063/5.0120103. The article is included in the thesis. Also available at: https://doi.org/10.1063/5.0120103 |
Paper III. J. García-Fernández, S. B. Kjeldby, L. J. Zeng, A. Azarov, A. Pokle, P. D. Nguyen, E. Olsson, L. Vines, A. Yu Kuznetsov, Ø. Prytz, ”In-situ atomic-resolution study of transformations in double polymorph γ/β-Ga2O3 structures”. Materials Advances. 2024, 5 (9), 3824-3831, DOI: 10.1039/D3MA01011B. The article is included in the thesis. Also available at: https://doi.org/10.1039/D3MA01011B |
Paper IV. S. B. Kjeldby, J. García-Fernández, A. Galeckas, I.J.T. Jensen, Ø. Prytz and L. Vines, ”Cross-sectional cathodoluminescence measurements of Cr-luminescence in implanted and annealed gallium oxide”, Submitted to: Journal of Applied Physics (2024). To be published. The paper is not available in DUO awaiting publishing. |
Paper V. S. B. Kjeldby, P. D. Nguyen, J. García-Fernández, K. Haug, A. Galeckas, I. J. T. Jensen, A. Thøgersen, L. Vines and Ø. Prytz, ”Optical properties of ZnFe2O4 nanoparticles and Fe-decorated inversion domain boundaries in ZnO”, Nanoscale Advances 5, 2102 (2023). DOI: 10.1039/D2NA00849A. The article is included in the thesis. Also available at: https://doi.org/10.1039/D2NA00849A |