Synthesis of thermally stable HfO_xN_y as gate dielectric for AlGaN/GaN heterostructure field-effect transistors

In this paper, we adopted thermally stable HfO_xN_y as gate dielectric for TiN/HfO_xN_y/AlGaN/GaN heterostructure field-effect transistors (HFETs) application. It demonstrated that the surface morphologies, composition, and optical properties of the HfO_xN_y films were dependent on oxygen flow rate in the O₂/N₂/Ar mixture sputtering ambient. The obtained metal-oxide-semiconductor heterostructure field-effect transistors by depositing HfO₂ and HfO_xN_y dielectric at different oxygen flow rates possessed a small hysteresis and a low leakage current. After post deposition annealing at 900 ℃, the device using HfO_xN_y dielectric operated normally with good pinch-off characteristics, while obvious degradation are observed for the HfO₂ gated one at 600 ℃. This result shows that the HfO_xN_y dielectric is a promising candidate for the self-aligned gate process.