Hydrogen-terminated diamond field-effect transistor with a bilayer dielectric of HfSiON/Al₂O₃

The fabrication of a single-crystal hydrogen-terminated diamond metal-oxide-semiconductor field-effect transistor (MOSFET) with HfSiON/Al₂O₃ bilayer dielectric has been carried out. HfSiON and Al₂O₃ layers were deposited by sputtering-deposition (SD) and atomic layer deposition (ALD) techniques. The maximum output current for SD-HfSiON/ALD-Al₂O₃ was 36 mA mm^-1, and for ALD-Al₂O₃, it was 31 mA mm^-1. We reported that the hysteresis shift voltage of the bilayer dielectric MOSFET was one fourth of the single dielectric layer MOSFET. The leakage current density of SD-HfSiON/ALD-Al₂O₃ was one order of magnitude lower than the single layer dielectric. We also determined the dielectric constants of HfSiON/Al₂O₃ and Al₂O₃ dielectrics based on capacitance-voltage characteristics. The values of V_TH, on/off ratio, subthreshold swing, and low field mobility for the bilayer dielectric MOSFET were evaluated to be 4.5 V, 10⁵, 296 mV/decade, and 154 cm² V^-1 s^-1, respectively.