This paper presents an overview of the different methods used for sensitivity (i.e., responsivity and noise equivalent power) determination of state-of-the-art field-effect transistor-based THz detectors/sensors. We point out that the reported result may depend very much on the method used to determine the effective area of the sensor, often leading to discrepancies of up to orders of magnitude. The challenges that arise when selecting a proper method for characterisation are demonstrated using the example of a 2×7 detector array. This array utilises field-effect transistors and monolithically integrated patch antennas at 620 GHz. The directivities of the individual antennas were simulated and determined from the measured angle dependence of the rectified voltage, as a function of tilting in the E- and H-planes. Furthermore, this study shows that the experimentally determined directivity and simulations imply that the part of radiation might still propagate in the substrate, resulting in modification of the sensor effective area. Our work summarises the methods for determining sensitivity which are paving the way towards the unified scientific metrology of FET-based THz sensors, which is important for both researchers competing for records, potential users, and system designers.

We report on circuit simulation, modeling, and characterization of field-effect transistor based terahertz (THz) detectors (TeraFETs) with integrated patch antennas for discrete frequencies from 1.3 to 5.7 THz. The devices have been fabricated using a standard 90-nm CMOS technology. Here, we focus in particular on a device showing the highest sensitivity to 4.75-THz radiation and its prospect to be employed for power monitoring of a THz quantum cascade laser used in a heterodyne spectrometer GREAT (German REceiver for Astronomy at Terahertz frequencies). We show that a distributed transmission line based detector model can predict the detector's performance better than a device model provided by the manufacturer. The integrated patch antenna of the TeraFET designed for 4.75 THz has an area of 13 × 13 µm 2 and a distance of 2.2 µm to the ground plane. The modeled radiation efficiency at the target frequency is 76% with a maximum directivity of 5.5, resulting in an effective area of 1750 µm 2. The detector exhibits an area-normalized minimal noise-equivalent power of 404 pW/ √ Hz and a maximum responsivity of 75 V/W. These values represent the state of the art for electronic detectors operating at room-temperature and in this frequency range.

We present a 24×24 pixel camera capable of high-speed THz imaging in power-detection mode. Each pixel of the sensor array consists of a pair of 150-nm NMOS transistors coupled to a patch antenna with resonance at 600 GHz. The camera can operate with a speed of up to 450 frames per second where it exhibits a minimum resolvable power of 10.5 nW per pixel. For a 30-Hz frame rate, the minimum resolvable power is 1.4 nW.

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