Carbon Nanotube Schottky Diode With Broadband Nonlinear Equivalent Circuit Model for Millimeter-Wave Frequency Multiplication

This letter presents a nonlinear model for carbon nanotube (CNT) Schottky diodes, integrating dc, small-signal, and large-signal parameters. A broadband equivalent model, spanning dc to 110 GHz, is proposed to meet the frequency requirements for millimeter-wave (mm-wave) frequency multiplication. A CNT Schottky diode with a 100-nm channel length was designed, fabricated, and measured, demonstrating good agreement with the model. The diode exhibited a maximum current of −7.7 mA, a cutoff frequency exceeding 180 GHz, and a conversion loss of 24 dB at 60 GHz with an input power of 13 dBm at 30 GHz. To the best of the authors’ knowledge, this is the first demonstration of CNT-based Schottky diodes for millimeter-wave frequency multiplication, supported by the model.