Ozone Surface Pretreatment for Enhanced β-Ga₂O₃/Dielectric Interface Engineering

The β-Ga₂O₃/Al₂O₃ gate-dielectric interface is systematically investigated following various oxidative surface treatments via in situ physical characterization and ex situ electrical device characterization. Although β-Ga₂O₃ surfaces pretreated with established oxidizing techniques (namely, O₂ plasma, ultraviolet-ozone [UV-O₃], and O₂ annealing) demonstrate a significant reduction in carbonaceous species via in situ X-ray photoelectron spectroscopy (XPS), capacitance-voltage (C-V) profiling of the corresponding metal-oxide-semiconductor (MOS) capacitors reveals no commensurate improvement in electrical performance. This discrepancy is attributed to the readsorption of carbonaceous species, presumably derived from residual metal-organic precursors, onto the semiconductor surface during thermal equilibration within the atomic layer deposition (ALD) chamber. In this work, we report an integrated O₃ prepulsing strategy designed to decontaminate the β-Ga₂O₃ surface immediately before dielectric deposition, thereby minimizing the exposure window to deleterious carbonaceous species within the ALD ambient. Compared to the alternative pretreatments, O₃ prepulsing yields superior surface passivation and decontamination, resulting in marked improvements in flat-band characteristics, interface trap density, and frequency dispersion. O₃ prepulsing is compatible with standard ALD systems and provides a practical, scalable solution for high-quality β-Ga₂O₃ gate-oxide engineering.