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

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic waves in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here, we report that such detectors based on AlGaN/GaN two-dimensional electron gas at 77K are able to sense 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 900GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0THz. The 900GHz detector at 77K offers an optical sensitivity about 1 pW/root 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. Published by AIP Publishing.