A 340 GHz Waveguide-Coupled GaN HEMT Terahertz Detector

Lens and waveguide integration are generally used to couple terahertz waves for terahertz detectors. Waveguide coupling provides a higher terahertz wave coupling efficiency compared to lens coupling which is beneficial to achieve a higher sensitivity. Previously, high-electron-mobility transistors (HEMT) terahertz detectors/mixers made of AlGaN/GaN heterostructure had to use lens coupling schemes due to their high impedance, which resulted in an impedance mismatch with the waveguides. This paper presents a waveguide coupling scheme including the design and simulation of a 340 GHz AlGaN/GaN HEMT terahertz detector. The detector design incorporates a waveguide-microstrip E-plane probe transition structure and a microstrip line impedance matching structure to reduce the impedance and improve the sensitivity. The simulation results show that the noise-equivalent power (NEP) of the terahertz detector can reach 29 pW/Hz1/2 and 21 pW/Hz1/2 at 340 GHz with the gate lengths of 1.0 μm and 0.8 μm for the HEMT mixer chip and the sensitivity can be further improved by shortening the gate length.