Abstract-Terahertz Detection With a Low-Cost Packaged GaAs High-Electron-Mobility Transistor

Elham Javadi,  Alvydas Lisauskas,  Mahmoud Shahabadi,  Nasser Masoumi , Jingshui Zhang, 
Johann Wolfgang Goethe

https://ieeexplore.ieee.org/document/8506393

We present experimental results of an investigation into the performance of a commercial, packaged GaAs high-electron-mobility transistor (HEMT) as a detector of terahertz (THz) radiation in the frequency ranges 0.22–0.32 and 0.520–0.650 THz. Enclosed in a standard ceramic housing and without a dedicated antenna for radiation coupling, the transistor is capable of sensitive direct detection (power detection) of THz radiation at room temperature. The device responsivity shows a strong variation with wavelength, indicating that various device features (transistor metallization, contact pads, wires) act as an effective THz antenna. With the THz radiation focused with a parabolic mirror (and without a substrate lens), the maximum responsivity reaches 2.5 and 0.72 V/W with values of the minimum optical noise-equivalent power (NEP) of 1.4 and 2.5 nW/ Hz−−−√ at the sensitivity peaks at 0.271 and 0.632 THz, respectively. The performance of the HEMT, in comparison with antenna-coupled FET detectors optimized for THz detection (TeraFETs), can be assessed better if the responsivity and the NEP are referred to the effective antenna cross-section determined experimentally for the device. We arrive at a cross-sectional responsivity of 42 V/W (1.6 V/W) and a cross-sectional NEP of 135 pW/ Hz−−−√ (1250  pW/ Hz−−−√ ) at 0.271 THz (0.632 THz), for measurements through the ceramic cap. The cross-sectional NEP values are about one order of magnitude at 0.271 THz and two orders of magnitude at 0.632 THz higher than those achieved with the best TeraFETs, yet in a range where they enable many practical applications at low cost for the detector.

Abstract-Continuous Wave Terahertz Sensing Using GaN HEMTs

Elham Javadi, Juan Antonio Delgado Notario, Nasser Masoumi, Y. M. Meziani, 

https://www.researchgate.net/publication/324264744_Continuous_Wave_Terahertz_Sensing_Using_GaN_HEMTs

A commercial GaN high electron mobility transistor (HEMT) is investigated as efficient detector of terahertz radiations. Enhancement of the photoresponse in excess of one order of magnitude (up to 1 kV W−1) is obtained when a constant drain‐to‐source current is applied. The photoresponse remains unchanged with chopping frequency up to 5 kHz demonstrating a high‐speed response of GaN HEMT detectors. It is demonstrated that the bounding wires play an important role to couple terahertz radiations to the channel of the device. Terahertz imaging of hidden objects by using GaN HEMTs as a sensor is also demonstrated. GaN high electron mobility transistor (HEMT) is used as an efficient detector of terahertz radiations with good responsivity. Terahertz imaging of hidden objects is obtained using the GaN HEMTs as a sensor. This open the way for new compact terahertz system for inspection and imaging applications.