Atomic-scale characterization of structural damage and recovery in Sn ion-implanted β-Ga2O3

beta-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of beta-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of beta-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted beta-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic beta-phase to the defective cubic spinel gamma-phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the gamma-Al2O3, which has the same space group as beta-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 < 110 > type in cubic structure. We show that post-implantation annealing at 1100 degrees C under the N-2 atmosphere effectively recovers the beta-phase; however, nano-sized voids retained within the beta-phase structure and a gamma-phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of beta-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability. Published under an exclusive license by AIP Publishing.