LAUSR

Abstract Fabrication of normally-off hydrogen-terminated diamond field-effect transistors (FET) has been carried out by using 3 nm Al2O3 dielectric layer, which was formed by thermally oxidizing 3 nm Al in air. 100 nm Al was covered on the 3 nm Al2O3 dielectric layer to form Al/Al2O3 gate. The leakage current density of FET with 6 μm gate length kept smaller than 5 × 10− 7 A·cm− 2, while the gate voltages swept from 3 to − 5 V. The capacitance-voltage characteristic indicated low-trapped charge densities in Al2O3 dielectric layer. For comparison, FET with only 3 nm Al2O3 gate and with 100 nm Al/3 nm Al2O3 gate was fabricated, which showed normally-on and normally-off characteristic respectively, indicating that 100 nm Al/3 nm Al2O3 gate could deplete hole densities in FET channel due to the difference of work function between Al and hydrogen-terminated diamond.