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

The effects of hydrogen plasma treatment of beta-Ga2O3 grown by halide vapor phase epitaxy and doped with Si are reported. Samples subjected to H plasma exposure at 330 degrees C developed a wide (similar to 2.5 mu m-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 beta-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-1.05eV. Annealing at 450 degrees C decreased the thickness of the depletion layer to 1.3 mu m at room temperature and moved the Fermi level pinning position to E-c-0.8eV. Further annealing at 550 degrees C almost restored the starting shallow donor concentration and the spectra of deep traps dominated by E-c-0.8eV and E-c-1.05eV 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.