Electromagnetic–Thermal Far-Infrared Detection Using Arrays of Schottky Barrier Diode Detectors in a Foundry CMOS Tuned at 20 Terahertz

A Schottky barrier diode with a cutoff frequency of ∼2 THz coupled to an antenna fabricated in foundry complementary metal–oxide–semiconductor (CMOS) is used for electromagnetic–thermal detection of far-infrared (FIR) signals. The reduction of aperture size with the operating frequency is mitigated by using a 4 × 4 array of parallel connected detectors. This increases the signal-to-noise ratio of the detected output signal by ∼10 dB while increasing noise equivalent power (NEP) by ∼3X. The lowest optical NEP and the highest optical responsivity (
R_v
) for the detector array of 484 nW/√Hz and 3 V/W are measured using a quantum cascaded laser (QCL) and an Agilent 89441A vector signal analyzer. A 4 × 4 array is utilized to form an image of a 10-Ω wire-wound resistor with temperatures ranging from 310 to 453 K, which were calibrated using an FLIR C3 camera. Finally, variations of low-frequency noise are a serious limitation and approaches to mitigate this are needed to realize
low-cost FIR detectors tuned at 20 THz that can be cointegrated with readout circuits.