Terahertz Detection at 240 GHz with a Semiconducting Carbon-Nanotube Field-Effect Transistor

We report on terahertz detection experiments at 240 GHz using carbon-nanotube field-effect transistors with a single semiconducting single-walled tube as the transistor's channel. From DC channel resistance measurements, the voltage response is predicted theoretically from the dc transconductance of the devices. Rectification is shown for an electronically applied 2-MHz signal and for free-space illumination at 240 GHz. The measured voltage responses compare well with the theory, however, at 240 GHz an additional gate-bias-dependent contribution to the rectified signal is observed for higher gate voltages.