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).

Abstract-Detection of incoherent broadband terahertz light using antenna-coupled high-electron-mobility field-effect transistors

Hua Qin, Xiang Li, Jiandong Sun, Zhipeng Zhang, Yunfei Sun, Yao Yu, Xingxin Li, Muchang Luo

(Submitted on 9 Mar 2017)

http://search.arxiv.org:8081/paper.jsp?r=1703.03128&qid=1494538993967ler_nCnN_318394178&qs=terahertz

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic wave in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here we report such detectors based on AlGaN/GaN two-dimensional electron gas at 77~K are able to sense broadband and incoherent terahertz radiation. The measured photocurrent as a function of the gate voltage agrees well with the self-mixing model and the spectral response is mainly determined by the antenna. A Fourier-transform spectrometer equipped with detectors designed for 340, 650 and 900~GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0~THz. The 900~GHz detector at 77~K offers an optical sensitivity about $1~\mathrm{pW/\sqrt{Hz}}$ being comparable to a commercial silicon bolometer at 4.2~K. By further improving the sensitivity, room-temperature detectors would find applications in active/passive terahertz imaging and terahertz spectroscopy.

Abstract-Room-temperature, low-impedance and high-sensitivity terahertz direct detector based on bilayer graphene field-effect transistor

• Hua Qin^1,, 
• Jiandong Sun¹, 
• Shixiong Liang², 
• Xiang Li^1, 3, 
• Xinxin Yang^1, †, 
• Zehao He², 
• Cui Yu²,
• Zhihong Feng^2, , 

• ¹ Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics (SINANO), Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou 215123, PR China
• ² National Key Laboratory of ASIC, Hebei Semiconductor Research Institute, Shijiazhuang, Hebei 050051, PR China
• ³ School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123, PR China
• 
  

http://www.sciencedirect.com/science/article/pii/S0008622317301653

We report a room-temperature, low-impedance and high-sensitivity terahertz direct terahertz detector based on bilayer graphene field-effect transistor (GFET). Epitaxially grown on silicon carbide, the bilayer graphene had an as-grown carrier mobility of 3000 cm²/Vs. The source/drain contacts were formed on the freshly cleaned graphene sheet to minimize the contact resistance and served also as terahertz antennas. The gate and the dielectric layer underneath with a length of 145 nm and a gap of 203 nm to the source/drain antennas were formed in a self-alignment process. Although the carrier mobility in the GFET was reduced to about 405 cm²/Vs, the high-quality ohmic contacts and the short graphene channel delivered an overall source-drain resistance less than 203 Ω. A voltage responsivity of 30 V/W and a noise-equivalent power of 51 pW/Hz^1/2were estimated in direct detection at 0.33 THz. By using the GFET detector as a two-terminal detector, i.e., with the gate floating, a transmission-type terahertz imaging was demonstrated. Such a low-impedance GFET detector is ready to be matched to a commercial 50-Ω low-noise radio/microwave frequency amplifier allowing for high-speed homodyne detection and heterodyne detection in a quasi-optical configuration.

Abstract-Applications

• Jiandong Sun

• http://link.springer.com/chapter/10.1007/978-3-662-48681-8_6

Nonresonant self-mixing terahertz detectors have a few advantages concerning the room-temperature operation, high sensitivity, wide response spectrum, high speed, and high signal-to-noise ratio over other slow bolometric detectors for room-temperature applications. Terahertz imaging based on single-pixel detectors and a 1×9 linear detector array are demonstrated with a high spatial resolution and a high signal-to-noise ratio. The single-pixel detector is successfully implemented in a Fourier transform spectrometer and a fast Fourier transform spectroscopy of a 900 GHz terahertz signal is demonstrated. Although the demonstrated self-mixing detectors are far from optimal in sensitivity, speed, stability, and reproducibility, this technology has a great potential to be further developed and optimized to bring many terahertz applications at room temperature into reality.