Optical Performance of Liquid Nitrogen Cooled Transistor-Based THz Detectors

We report on the improvement of the optical performance of THz detectors based on antenna-integrated Si CMOS field-effect transistors (TeraFETs) when cooled with liquid nitrogen (temperature range 77-297 K). The minimum optical noise-equivalent power (NEP) at 77 K is as low as 11.7 pW/√Hz at 0.6 THz, which corresponds to a decrease by a factor of 3.8 compared to room temperature, and approaching the optical sensitivity levels of commercial helium-cooled bolometers. The channel's static resistance, optical responsivity and NEP measurements reveal a specific feature for this family of detectors. There are gate biasing regimes for which the selected performance parameter can be maintained almost independent of the temperature. This feature is desirable in applications requiring stability from the variations in the environmental conditions.