Atomic scale defect formation and phase transformation in Si implanted β-Ga2O3

Atomic scale details of the formation of point defects and their evolution to phase transformation in silicon (Si) implanted beta-Ga2O3 were studied using high resolution scanning transmission electron microscopy (STEM). The effect of Si implantation and the formation of defects was studied as a function of the dose of implanted atoms, and the detailed mechanism of lattice recovery was observed using both in situ and ex situ annealing of the implanted beta-Ga2O3. The implantation created nanoscale dark spots in STEM images, which we identified as local gamma-Ga2O3 inclusions generated by the relaxation of lattice due to (010) screw dislocations created by the implantation. The number and size of gamma-Ga2O3 regions increased as the Si dose increased, and eventually the gamma-Ga2O3 crystal phase (with stacking defects) took over the entire implanted volume when the peak Si concentration was over similar to 10(20) cm(-3). Annealing above 1100 degrees C disintegrates the local gamma-Ga2O3 phase and returns the structure to defect-free, single crystal beta phase, likely indicating that point defects (such as Si interstitials and cation vacancies) are spatially redistributed by the annealing. However, when the structure is completely transformed to gamma-Ga2O3 by the implantation, post-annealing leaves a high concentration of dislocations within the beta phase, which relates to the inhomogeneous distribution of Si atoms detected by secondary ion mass spectrometry. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).