# Time resolution and dynamic range of field effect transistor based terahertz detectors

## TL;DR

This study demonstrates that various field effect transistor-based terahertz detectors have nanosecond response times, broad dynamic ranges, and power-dependent saturation behaviors, making them suitable for high-power pulsed THz applications.

## Contribution

The paper provides a comparative analysis of different FET-based THz detectors, revealing their fast response, linearity, and saturation characteristics across a range of frequencies and powers.

## Key findings

- Detectors have at least nanosecond response time.
- Response remains linear over a wide power range before saturation.
- Saturation power and responsivity depend on frequency as P_s ∝ f^3 and R_0 ∝ f^{-3}.

## Abstract

We studied time resolution and response power dependence of three terahertz detectors based on significantly different types of field effect transistors. We analyzed the photoresponse of custom-made Si junctionless FETs, Si MOSFETs and GaAs-based high electron mobility transistors detectors. Applying monochromatic radiation of high power, pulsed, line-tunable molecular THz laser, which operated at frequencies in the range from 0.6-3.3 THz, we demonstrated that all these detectors have at least nanosecond response time. We showed that detectors yield a linear response in a wide range of radiation power. At high powers the response saturates varying with radiation power P as $U = R_0 P/(1+P/P_s)$, where $R_0$ is the low power responsivity, $P_s$ is the saturation power. We demonstrated that the linear part response decreases with radiation frequency increase as $R_0 \propto f^{-3}$, whereas the power at which signal saturates increases as $P_s \propto f^3$. We discussed the observed dependences in the framework of the Dyakonov-Shur mechanism and detector-antenna impedance matching. Our study showed that FET transistors can be used as ultrafast room temperature detectors of THz radiation and that their dynamic range extends over many orders of magnitude of power of incoming THz radiation. Therefore, when embedded with current driven read out electronics they are very well adopted for operation with high power pulsed sources.