Structural transition and recovery of Ge implanted β-Ga2O3

• Published in: Applied physics letters Vol. 117; no. 15
• Main Authors: Anber, Elaf A., Foley, Daniel, Lang, Andrew C., Nathaniel, James, Hart, James L., Tadjer, Marko J., Hobart, Karl D., Pearton, Stephen, Taheri, Mitra L.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 12.10.2020; American Institute of Physics (AIP)
• Subjects: Analytical electron microscopy; Annealing; Applied physics; Damage; Electron diffraction; Electron energy loss spectroscopy; Electron microscopy; Energy dissipation; Fine structure; Fluence; Gallium oxides; Ion implantation; MATERIALS SCIENCE; Microscopy; Phase transitions; Physics; Recovery; Spectrum analysis; Strain analysis; Tensile strain; Ultrawide Bandgap Semiconductors
• ISSN: 0003-6951; 1520-8842; 1077-3118; 1077-3118
• DOI: 10.1063/5.0022170

Ion implantation-induced effects were studied in Ge implanted β-Ga2O3 with the fluence and energy of 3 × 1013 cm−2/60 keV, 5 × 1013 cm−2/100 keV, and 7 × 1013 cm−2/200 keV using analytical electron microscopy via scanning/transmission electron microscopy, electron energy loss spectroscopy, and precession electron diffraction via TopSpin. Imaging shows an isolated band of damage after Ge implantation, which extends ∼130 nm from the sample surface and corresponds to the projected range of the ions. Electron diffraction demonstrates that the entirety of the damage band is the κ phase, indicating an implantation-induced phase transition from β to κ-Ga2O3. Post-implantation annealing at 1150 °C for 60 s under the O2 atmosphere led to a back transformation of κ to β; however, an ∼17 nm damage zone remained at the sample surface. Despite the back transformation from κ to β with annealing, O K-edge spectra show changes in the fine structure between the pristine, implanted, and implanted-annealed samples, and topspin strain analysis shows a change in strain between the two samples. These data indicate differences in the electronic/chemical structure, where the change of the oxygen environment extended beyond the implantation zone (∼130 nm) due to the diffusion of Ge into the bulk material, which, in turn, causes a tensile strain of 0.5%. This work provides a foundation for understanding of the effects of ion implantation on defect/phase evolution in β-Ga2O3 and the related recovery mechanism, opening a window toward building a reliable device for targeted applications.