# Detection of incoherent broadband terahertz light using antenna-coupled high-electron-mobility field-effect transistors

## TL;DR

This paper demonstrates broadband incoherent terahertz detection using AlGaN/GaN HEMT-based detectors at 77K, achieving sensitivities comparable to cooled bolometers and enabling terahertz spectroscopy from 0.1 to 2.0 THz.

## Contribution

The study introduces high-electron-mobility transistors as broadband terahertz detectors with sensitivity near that of traditional bolometers, operating at 77K.

## Key findings

- Detectors operate effectively at 77K for broadband terahertz detection.
- Spectral response is primarily determined by the antenna design.
- Sensitivity comparable to silicon bolometers at cryogenic temperatures.

## Abstract

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic wave in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here we report such detectors based on AlGaN/GaN two-dimensional electron gas at 77~K are able to sense broadband and incoherent terahertz radiation. The measured photocurrent as a function of the gate voltage agrees well with the self-mixing model and the spectral response is mainly determined by the antenna. A Fourier-transform spectrometer equipped with detectors designed for 340, 650 and 900~GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0~THz. The 900~GHz detector at 77~K offers an optical sensitivity about $1~\mathrm{pW/\sqrt{Hz}}$ being comparable to a commercial silicon bolometer at 4.2~K. By further improving the sensitivity, room-temperature detectors would find applications in active/passive terahertz imaging and terahertz spectroscopy.