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.

Abstract-Passive terahertz imaging detectors based on antenna-coupled high-electron-mobility transistors

Jiandong Sun, Yifan Zhu, Wei Feng, Qingfeng Ding, Hua Qin, Yunfei Sun, Zhipeng Zhang, Xiang Li, Jinfeng Zhang, Xinxing Li, Yang Shangguan, and Lin Jin

 (a) Scanning-electron micrograph of the detector with schematic measurement circuitry. (b) Zoom-in view of the central active region including the gate and the field-effect channel. (c, d) Backside and front-side views of the silicon hyperhemispherical lens with a detector chip assembled on the planar surface in a liquid nitrogen dewar with a TPX window.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-4-4911

Aiming at the requirement of passive terahertz imaging, we report a high-sensitivity terahertz detector based on an antenna-coupled AlGaN/GaN high-electron-mobility transistor (HEMT) at 77 K without using low-noise terahertz amplifier. The measured optical noise-equivalent power and the noise-equivalent temperature difference of the detector were about 0.3pW/Hz−−−√$0.3\mathrm{p}\mathrm{W}/\sqrt{\mathrm{H}\mathrm{z}}$ and 370 mK in a 200 ms integration time over a bandwidth of 0.7 − 0.9 THz, respectively. By using this detector, we demonstrated passive terahertz imaging of room-temperature objects with signal-to-noise ratio up to 13 dB. Further improvement in the sensitivity may allow passive terahertz imaging using AlGaN/GaN-HEMT at room temperature.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Two-terminal terahertz detectors based on AlGaN/GaN high-electron-mobility transistors

Applied Physics Letters

Jiandong Sun, Zhipeng Zhang,  Xiang Li, Hua Qin, Yunfei Sun, Yong Cai, Guohao Yu, Zhili Zhang, Jinfeng Zhang, Yang Shangguan, Lin Jin, Xinxing Li, Baoshun Zhang,  V. V. Popov,

(a) A top view of the detector. (b) Central gate and fluorine ion implantation area of the detector. (c) A schematic cross section of the detector corresponding to the dotted red line in (b). (d) A color-scale 2D plot of the spatial distribution of the mixing factor from a FDTD simulation at 648 GHz.

https://aip.scitation.org/doi/abs/10.1063/1.5114682

We report an approach to make two-terminal antenna-coupled AlGaN/GaN high-electron-mobility-transistor self-mixing terahertz detectors. Fluorine ion implantation is used to increase the threshold voltage of the AlGaN/GaN two-dimensional electron gas. An optimal implantation dose can be reached so that the detector responsivity is maximized at zero gate voltage or with the gate floating. The relationship between the ion dosage and the threshold voltage, electron mobility, electron density, responsivity, and noise-equivalent power (NEP) is obtained. A minimum optical NEP of 47  W/Hz⎯⎯⎯⎯⎯√$47\hspace{0.17em}\hspace{0.17em}\mathrm{W}/\sqrt{\text{Hz}}$ is achieved from a two-terminal detector at 0.65 THz. The capability of two-terminal operation allows for the design of a large array of antenna-coupled high-electron-mobility transistor detectors without the demanding needs of routing negative gate voltage lines around the antenna array and minimizing the gate leakage current.

The authors acknowledge support from the National Key Research and Development Program of China (No. 2016YFF0100501), the China National Natural Science Foundation (Nos. 61771466 and 61775231), the Youth Innovation Promotion Association CAS (No. 2017372), the Six Talent Peaks Project of Jiangsu Province, China (No. XXRJ-079), and the Russian Foundation for Basic Research (No. 17-52-53063).