AlGaN/GaN HEMT Sub-Terahertz Detectors Integrated with Spiral Antennas

This paper presents a study of an AlGaN/GaN high electron mobility transistor (HEMT) terahertz detector integrated with a planar spiral antenna. The proposed device is designed to operate in the backward wave oscillator (BWO) fundamental frequency range of 175-385 GHz, which is important for various applications such as security checking, medical imaging, and communications. The spiral antenna is used to efficiently couple THz radiation into the detector, and the AlGaN/GaN HEMT is used as the sensing element. The proposed device was designed and simulated using commercial software Comsol and Silvaco TCAD. The simulation results show that the device has the maximum responsivity of 2197.5 V/W at 208 GHz, and exhibit good absorption rates at 206-211 GHz and 296-299 GHz. Optimizing the integration method by transitioning from source-drain integration to gate-source integration enhances the asymmetry of detector, thereby improving responsivity to 3500 V/W and increasing bandwidth to 230-255, 285-305 and 360-385 GHz, the multi-band response characteristic is mainly attributed to the specially designed spiral antenna. In addition, the effects of antenna size and shape on the device performance were investigated through simulation. It was found that the spiral structure provides better performance compared to the bow-tie structure in our previous work, and increasing the antenna size can improve the characteristics of responsivity and noise equivalent power (NEP). The proposed device has the potential to be a promising candidate for future THz sensing applications due to its high responsivity, broad bandwidth, low NEP, good linearity and compact size.