Rational design of high-responsivity detectors of terahertz radiation based on distributed self-mixing in silicon field-effect transistors

Abstract

In search of novel detectors of electromagnetic radiation at terahertz frequencies, field-effect transistors (FETs) have recently gained much attention. The current literature studies them with respect to the excitation of plasma waves in the two-dimensional channel. Circuit aspects have been taken into account only to a limited degree. In this paper, we focus on embedding silicon FETs in a proper circuitry to optimize their responsivity to terahertz radiation. This includes impedance-matched antenna coupling and amplification of the rectified signal. Special attention is given to the investigation of high-frequency short-circuiting of the gate and drain contacts by a capacitive shunt, a common approach of high-frequency electronics to induce resistive mixing in transistors. We theoretically study the effect of shunting in the framework of the Dyakonov–Shur plasma-wave theory, with the following key results. In the quasistatic limit, the capacitive shunt induces the longitudinal high-frequency field needed in the FET’s channel for resistive mixing. In the non-quasi-static case, the shunt’s role is taken over by plasma waves. Rectification can then be described as distributed self-mixing in the transistor’s channel. Based on such considerations as well as other circuit-related aspects, we arrive at a rational design for FET-based detectors of terahertz radiation, and implement the first monolithically integrated 0.65 THz focal-plane array including antennas and amplifiers on a single silicon die. The measured performance data compare well with the theoretical predictions.

Ultra Low Noise CMOS Image Sensors

“…Under THz excitation, the non-quasi-static behaviour has to be considered. Distributed resistive self mixing extends the classic resistive self mixing theory [117,118]. It consists in the division of the channel into small RC segments.…”

Wide modulation bandwidth terahertz detection in 130 nm CMOS technology

“…It has also been described as a distributed self mixing resistive mixer [23] and by a lumped element approach for the region where the induced AC current exists [24]. A complete analytical expression valid in all regions of operation of the FET including sub-threshold, linear and saturation as well as the loading effect has been proposed in references [25,26].…”

“…Now, according to the self-mixing resistive mixer [23] model of FET-based detector, the output at the detector can be expressed in a simplified form as the square of the input signal. Thus, the detector essentially works as a power detector.…”

Tunable, continuous-wave Terahertz photomixer sources and applications

“…11 To date, many THz spectroscopic results were achieved with pulsed systems, mostly implementing LT-GaAs photomixers (THz-TDS). One reason for the choice of pulsed operation is the ease of detection of signals with extremely low intensity using electro-optic sampling or a zero-biased LT-GaAs [165][166][167] The latter four detection schemes operate at room temperature and can easily be miniaturized. They allow for extremely high chopping frequencies (up to more than 1 MHz) and, hence, short lock-in time constants and high measurement speed, enabling short data acquisition times.…”