Implementation of a multi-element detector consisting of an 8x8 network of patch-antenna-coupled TeraFETs for gas spectroscopy with THz-QCLs

Monolithically integrated, antenna-coupled field-effect transistors (TeraFETs) are known as sensitive detectors, which can be designed to work properly over the entire THz range (0.1-10 THz). In this work, we present a new multi-element THz detector design. It employs $8 \times 8$ monolithically integrated patch-antenna-coupled TeraFETs fabricated in a commercial 65-nm CMOS process. In contrast to conventional detector matrices, where each TeraFET represents a pixel, here the entire TeraFET network serves as a single pixel, combining the output signals of all elements in a parallel read-out circuit. The matrix approach offers two advantages: A larger effective detector area, which makes beam alignment easier, and a significantly reduced electrical resistance down to approx. 300 at the working bias point, leading not only to a reduction in detector noise but also to an increase in achievable modulation bandwidth, which improves the time resolution of measurements of dynamical processes. We demonstrate applicability of the detector for laboratory methanol vapor gas spectroscopy at 3.4 THz with a quantum cascade laser (QCL) applied as a radiation source.