Description
Interfacial defect states fundamentally limit the performance and reliability of β-Ga2O3 ultra-wide bandgap power devices. However, traditional electrical metrology cannot resolve the precise atomistic chemical origins and topological structures of these interfacial traps. Here, we orthogonalize and decouple chemical and topological surface defects using in-situ polarization-resolved Sum Frequency Generation (SFG) spectroscopy. By rationally combining chemical etching, selective plasma treatments, and thermal annealing, we identify two distinct localized optical signatures. We assign the 640 cm-1 mode to Ga-O stretching vibrations perturbed by adjacent oxygen vacancies (VO), and the 660 cm-1 mode to the step-edge and low-coordinated structural motifs. Furthermore, we directly correlate these microscopic probes with macroscopic device metrics: O2 annealing completely heals VO eliminating Fermi-level pinning and drastically reducing interface state density (Dit). Conversely, N2 annealing induces a high-density two-dimensional electron gas verified by a hot-electron-driven continuous background. These findings provide unprecedented optical fingerprints for complex defect architectures, establishing a non-destructive atomic-scale paradigm for interface passivation in next-generation electronics.
