8x8 Patch-Antenna-Coupled TeraFET Detector Array for Terahertz Quantum-Cascade-Laser Applications

Monolithically integrated, antenna-coupled fieldeffect transistors (TeraFETs) are rapid and sensitive detectors for the terahertz range (0.3-10 THz) that can operate at room temperature. We conducted experimental characterizations of a singlepatch-antenna-coupled TeraFET optimized for 3.4 THz operation and its integration into an 8x8 multielement detector configuration. In this configuration, the entire TeraFET array operates as a unified detector element, combining the output signals of all detector elements. Both detectors were realized using a mature commercial Si-CMOS 65-nm process node. Our experimental characterization employed single-mode quantum-cascade lasers (QCLs) emitting at 2.85 and 3.4 THz. The 8x8 multielement detector yields two major improvements for sensitive power detection experiments. First, the larger detector area simplifies alignment and enhances signal stability. Second, the reduced detector impedance enabled the implementation of a TeraFET+QCL system capable of providing a-3 dB modulation bandwidth up to 21 MHz, which is currently limited primarily by the chosen readout circuitry. Finally, we validate the system's performance by providing high-resolution gas spectroscopy data for methanol vapor around 3.4 THz, where a detection limit of 1.6 x 10(-5) absorbance or 2.6 x 10(11) molecules/cm(3) was estimated.