Hydrogen-Terminated Diamond Field-Effect Transistors With 1011 ON/ OFF Ratio Using an Al2O3/HfO2 Stacked Passivation Layer

Diamond-based devices with high ON/ OFF ratio are promising candidates for power and sensor applications. However, the limited ON/ OFF ratio caused by relatively high leakage currents still remains to be a problem. Herein, we present hydrogen-terminated diamond metal–insulator–semiconductor field-effect transistors (MISFETs) with a 40-/100-nm aluminum oxide/hafnium dioxide stacked passivation layer to reduce leakage currents. Due to the stacked passivation layer, the fringing capacitances were introduced and the electric field at the drain edge of the gate was reduced. Encouragingly, the drain and gate leakage currents were reduced to the order of $10^{-{9}}$ mA/mm under OFF-state conditions at room temperature. Consequently, an ON/ OFF ratio of $\sim 1\times 10^{{11}}$ was achieved, which is the highest value among the previously reported diamond-based field-effect transistors (FETs). Moreover, a record ON/ OFF ratio of $\sim 5\times 10^{{9}}$ was obtained even at 200 °C. Results of this work can pave the way for diamond-based devices in power or sensor applications.