Effects of fluorine-based plasma treatment and thermal annealing on high-Al content AlGaN Schottky contact

Fluorine plasma treatment was used prior to the Schottky metal deposition on the undoped Al_0.45Ga_0.55N, which aimed at the solar-blind wavelength. After fluorine plasma treatment and before depositing the Ni/Au Schottky, the samples were thermal annealed in the N₂ gas at 400℃. The reverse leakage current density of Al_0.45Ga_0.55N Schottky diode was reduced by 2 orders of magnitude at -10 V. The reverse leakage current density was reduced by 3 orders of magnitude after thermal annealing. Further capacitance-frequency analysis revealed that the fluorine-based plasma treatment reduces the surface states of AlGaN by one order of magnitude at different surface state energies. The capacitance-frequency analysis also proved that the concentration of carriers in AlGaN top is reduced through fluorine plasma treatment.