Above 300 GHz Ultrafast Cutoff Frequency Achieved via Air Gap-Induced Capacitance in van der Waals ReSe2 Schottky Diodes

초록

Sub-terahertz ultrahigh cutoff frequencies (fC) are achieved from a van der Waals material rhenium diselenide (ReSe2)-based vertical Schottky diode, when the diode architecture is specially designed with an air gap between 100 nm-thick ReSe2 and Ohmic contact electrode. The maximum intrinsic fC of our diode reaches 430 GHz, the highest among the reported thin film-based RF diodes. With the increase of air gap size, the intrinsic fC of each diode rises from similar to 30 GHz (without an air gap) to 310-430 GHz. The extrinsic fC, measured from RF rectifier circuits using the air gap-containing Schottky diode, also increases from 2 to 40 GHz. The underlying principle behind these fC enhancements is investigated using an equivalent circuit model, which closely matches the experimental results. Our air gap engineering provides a practical strategy to improve the fC of vertical Schottky diodes, opening new avenues for 2D material-based RF electronics.