Performance enhancement of CMOS terahertz detector by drain current

In this paper, we study the effect of the drain current on terahertz detection for Si metal-oxide semiconductor field-effect transistors (MOSFETs) both theoretically and experimentally. The analytical model, which is based on the small-signal equivalent circuit of MOSFETs, predicts the significant improvement of the voltage responsivity R_v with the bias current. The experiment on antennas integrated with MOSFETs agrees with the analytical model, but the R_v improvement is accompanied first by a decrease, then an increase of the low-noise equivalent power (NEP) with the applied current. We determine the tradeoff between the low-NEP and high-R_v for the current-biased detectors. As the best-case scenario, we obtained an improvement of about six times in R_v without the cost of a higher NEP. We conclude that the current supply scheme can provide high-quality signal amplification in practical CMOS terahertz detection.