Gate controllability of HfSiOx/AlGaN/GaN MOS high-electron-mobility transistor

Hafnium silicate (HfSiOx) has been applied to AlGaN/GaN high-electron-mobility transistors (HEMTs) as a high κ gate dielectric. The (HfO2)/(SiO2) laminate structure was deposited on the AlGaN surface by a plasma-enhanced atomic layer deposition, followed by a post-deposition annealing at 800 °C. The HfSiOx-gate HEMT showed good transfer characteristics with a high transconductance expected from its κ value and a subthreshold swing of 71 mV/decade. For the metal–oxide-semiconductor (MOS) HEMT diode, we observed excellent capacitance–voltage (C–V) characteristics with negligible frequency dispersion. The detailed C–V analysis showed low state densities on the order of 1011 cm−2 eV−1 at the HfSiOx/AlGaN interface. In addition, excellent operation stability of the MOS HEMT was observed at high temperatures up to 150 °C.