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 kappa 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 degrees C. The HfSiOx-gate HEMT showed good transfer characteristics with a high transconductance expected from its kappa 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 10(11) 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 degrees C.