Partners

Abstract:
The microscopic fate of dopants introduced under nonequilibrium conditions remains largely unresolved in wide-band gap oxides. Using temperature-dependent N K-edge X-ray absorption spectroscopy, we directly resolve the local bonding configuration of implanted nitrogen in (100) β-Ga2O3. The spectra are dominated by a sharp π* resonance characteristic of N≡N bonding that systematically intensifies upon annealing, providing a direct spectroscopic fingerprint of molecular nitrogen formation. First-principles calculations and multiple-scattering simulations reproduce these spectral features and identify molecular N2 as the dominant dopant state. Rather than forming substitutional acceptors, implanted nitrogen evolves toward N2-like configurations stabilized in defect-rich environments associated with local β→γ-like structural motifs. This behavior reflects a thermally driven reconfiguration of nitrogen within the damaged layer. These results demonstrate that dopant incorporation can proceed via molecularization pathways that bypass conventional substitutional doping, providing a general mechanism for dopant deactivation under nonequilibrium incorporation conditions in oxides.

Abstract:
Doping of β-Ga2O3 (100) with Si by ion implantation onto heated substrates is investigated. The study reveals complex ion beam-induced defect processes in β-Ga2O3, characterized by the formation of various defect types and their temperature-dependent transformation. By employing X-Ray Diffraction, Rutherford Backscattering Spectrometry, Particle-Induced X-Ray Emission, X-ray Absorption Near Edge Structure Spectroscopy, Transmission Electron Microscopy, and Density Functional Theory analyses, we examine lattice deformation, identify the local environment of dopants, assess electronic structure modifications, and verify the presence of extended defects induced by ion implantation. Our findings highlight the predominant contribution of substitutional and interstitial Si ions incorporated into complexes that act as donors manifesting n-type conductivity, while some fraction of the defects form complexes that act as traps for charge carriers. Notably, no monoclinic phase transformations were observed during implantation despite substrate temperature variations from 300 to 800 °C.

Keywords:
β-Ga2O3, WBG, Implantation, XRD, RBS/PIXE/c, XANES, TEM, DFT, FMS