Impact of Hydrogen Plasma on Electrical Properties and Deep Trap Spectra in Ga₂O₃ Polymorphs

In this study, the results of hydrogen plasma treatments of beta-Ga2O3, alpha-Ga2O3, kappa-Ga2O3 and gamma-Ga2O3 polymorphs are analyzed. For all polymorphs, the results strongly suggest an interplay between donor-like hydrogen configurations and acceptor complexes formed by hydrogen with gallium vacancies. A strong anisotropy of hydrogen plasma effects in the most thermodynamically stable beta-Ga2O3 are explained by its low-symmetry monoclinic crystal structure. For the metastable, alpha-, kappa- and gamma-polymorphs, it is shown that the net result of hydrogenation is often a strong increase in the density of centers supplying electrons in the near-surface regions. These centers are responsible for prominent, persistent photocapacitance and photocurrent effects.