Static Non-Linearity Based Analysis of Non-Resonant MOSFET as THz Detector

TL;DR

This paper analyzes the static non-linearities of CMOS FETs to understand their THz detection capabilities, highlighting the importance of second order effects, bias conditions, and device design for optimizing responsivity and noise performance.

Contribution

It introduces a static non-linearity based analysis method for non-resonant MOSFET THz detectors, emphasizing the role of second order effects and design tradeoffs.

Findings

Second order non-linearities dominate the DC response at THz frequencies.

Differential detector topology offers highest responsivity in cold operation.

Tradeoffs between channel resistance and load impedance affect detection performance.

Abstract

The non-resonant THz response of CMOS FET has been analyzed based on static non-linearities of the transistor channel. Under the quasi-static limit, the second order non-linearities dominantly determine the DC current in the channel generated in response to THz signal. For the applied gate-to source and drain-to-source signals, the significance of the second order non-linear terms is analyzed as a function of DC bias conditions. Based on the analysis, it has also been shown that a differential detector topology can give highest responsivity in cold operation. A tradeoff between the channel resistance and load impedance plays a vital role in detecting the generated current. Moreover, the design considerations such as readout modes, optimum bias points and device dimensions are also discussed with respect to both responsivity and noise equivalent power (NEP).