Abstract-Smaller antenna-gate gap for higher sensitivity of GaN/AlGaN HEMT terahertz detectors

Applied Physics Letters

Zhipeng Zhang, Xiang Li, Hua Qin, Jinfeng Zhang, Xinxing Li, Yang Shangguan, Lin Jin, Yunfei Sun, V. V. Popov,

(a) Schematic diagram of the GaN/AlGaN HEMT detector including the measurement circuit. (b) Zoom-in view of the central active region.

https://aip.scitation.org/doi/abs/10.1063/1.5142436

We report an attempt to improve the sensitivity of terahertz detection based on self-mixing in antenna-coupled field-effect transistors by enhancing the field-effect factor and the antenna factor with a reduced gate length and a reduced antenna-gate gap, respectively. An optical noise equivalent power (NEP) of 3.7 pW/Hz⎯⎯⎯⎯⎯√$3.7\hspace{0.17em}\text{pW}/\sqrt{\text{Hz}}$ at 0.65 THz was achieved in a GaN/AlGaN high-electron-mobility transistor (HEMT) with a gate length of 300 nm and an antenna-gate gap of 200 nm at room temperature. It was found that the antenna factor was inversely proportional to the antenna-gate gap, and the responses upon coherent/incoherent terahertz irradiation were well described by the self-mixing model. To fill the NEP gap of 0.1−1 pW/Hz⎯⎯⎯⎯⎯√$0.1-1\hspace{0.17em}\text{pW}/\sqrt{\text{Hz}}$ between room-temperature and cryogenic detectors by HEMT-based detectors at room temperature, impedance match needs to be carefully considered.

The authors acknowledge support from the National Natural Science Foundation of China (Nos. 61771466, 61775231, and 61975227), the Youth Innovation Promotion Association CAS (No. 2017372), the Six Talent Peaks Project of Jiangsu Province, China (XXRJ-079), and the Russian Foundation for Basic Research (No. 17-52-53063). The work in the Kotelnikov IRE RAS was carried out within the framework of the state task.