AlGaN/GaN high electron mobility transistors on Si with sputtered TiN gate

AlGaN/GaN high electron mobility transistors (HEMTs) on Si were fabricated and studied using sputtered TiN Schottky gate. The sputtered TiN on AlGaN/GaN HEMTs exhibit an improved Schottky barrier height (SBH) of approximate to 1.1eV, which is larger than the Schottky contacts formed by the other reported TiN-based stacks and by most of Ni/Au-free materials. The improvement of SBH is due to the increase of metal work function either by the incorporation of oxygen in sputtered TiN or by using a high N-2/Ar ratio during the sputtering process. Although the HEMTs with TiN gate show comparable DC output and transfer characteristics compared to devices with Ni/Au gate, they exhibit enhanced OFF-state breakdown voltages (BVgd) of approximate to 48-58V. This is consistent with the observation of an order of magnitude lower reverse gate leakage current and is also well agreed by the enhanced SBH of the sputtered TiN as compared to the Ni/Au gate. With reference to the HEMTs with Ni/Au gate, a slight increase of dynamic/static on-resistances (R-ds[ON]) ratio (approximate to 8%) was observed in the sputtered TiN gate HEMTs.