Identification and Suppression of Majority Surface States in the Dry-Etched β-Ga₂O₃

Surface treatment after dry etching is vital to enhance the surface quality of the material and thus improve device performance. In this Letter, we identified the majority surface states induced by the dry etching of β-Ga₂O₃ and optimized surface treatments to suppress these electrically active defects with the improved performance of Schottky barrier diodes. Transient spectroscopies suggested that the majority traps (E_C-0.75 eV) related to divacancies (V_Ga-V_O) were enhanced in the concentration of 3.37 × 10¹⁴ cm^-3 by dry etching and reduced to 0.90 × 10¹⁴ cm^-3 by the combined means of oxygen annealing and piranha solution treatment. The trap evolution is supported by the suppressed donor-acceptor pair radiative recombination related to oxygen vacancies, the improved carrier transport (negligible hysteresis current-voltage and unity ideality factor), and the reduced surface band bending. These findings provide a straightforward strategy to improve surface quality for the further performance improvement of Ga₂O₃ power diodes.