Hydrogen plasma treatment of β -Ga₂O₃: Changes in electrical properties and deep trap spectra

The effects of hydrogen plasma treatment of β-Ga₂O₃ grown by halide vapor phase epitaxy and doped with Si are reported. Samples subjected to H plasma exposure at 330 °C developed a wide (∼2.5 μm-thick) region near the surface, depleted of electrons at room temperature. The thickness of the layer is in reasonable agreement with the estimated hydrogen penetration depth in β-Ga₂O₃ based on previous deuterium profiling experiments. Admittance spectroscopy and photoinduced current transient spectroscopy measurements place the Fermi level pinning position in the H treated film near E_c-1.05 eV. Annealing at 450 °C decreased the thickness of the depletion layer to 1.3 μm at room temperature and moved the Fermi level pinning position to E_c-0.8 eV. Further annealing at 550 °C almost restored the starting shallow donor concentration and the spectra of deep traps dominated by E_c-0.8 eV and E_c-1.05 eV observed before hydrogen treatment. It is suggested that hydrogen plasma exposure produces surface damage in the near-surface region and passivates or compensates shallow donors.