Ozone Surface Pretreatment for Enhanced β-Ga ₂ O ₃ /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.