Sensitive Terahertz Detection and Imaging Driven by the Photothermoelectric Effect in Ultrashort-Channel Black Phosphorus Devices

Wanlong Guo; Zhuo Dong; Yijun Xu; Changlong Liu; Dacheng Wei; Libo Zhang; Xinyao Shi; Cheng Guo; Huang Xu; Gang Chen; Lin Wang; Kai Zhang; Xiaoshuang Chen; Wei Lu

doi:10.1002/advs.201902699

Sensitive Terahertz Detection and Imaging Driven by the Photothermoelectric Effect in Ultrashort-Channel Black Phosphorus Devices

Adv Sci (Weinh). 2020 Jan 19;7(5):1902699. doi: 10.1002/advs.201902699. eCollection 2020 Mar.

Authors

Wanlong Guo^{1

2

3}, Zhuo Dong^{4

5}, Yijun Xu⁴, Changlong Liu⁶, Dacheng Wei⁷, Libo Zhang^{1

2

3}, Xinyao Shi⁴, Cheng Guo^{1

2}, Huang Xu^{1

2}, Gang Chen^{1

2}, Lin Wang^{1

2}, Kai Zhang⁴, Xiaoshuang Chen^{1

2

3}, Wei Lu^{1

2

3}

Affiliations

¹ State Key Laboratory of Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences 500 Yu-Tian Road Shanghai 200083 China.
² University of Chinese Academy of Sciences No. 19A Yuquan Road Beijing 100049 China.
³ School of Physical Science and Technology ShanghaiTech University Shanghai 201210 China.
⁴ CAS Key Laboratory of Nano-Bio Interface and Key Laboratory of Nanodevices and Applications i-Lab Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO) Chinese Academy of Sciences Ruoshui Road 398 Suzhou Jiangsu 215123 China.
⁵ School of Nano Technology and Nano Bionics University of Science and Technology of China Jinzhai Road 96 Hefei Anhui 230026 China.
⁶ Zhejiang Lab Artificial Intelligence Town No.1818 Wenyixi Road Hangzhou 311100 China.
⁷ Institute of Molecular Materials and Devices Department of Material Sciences and Department of Macromolecular Sciences Fudan University Shanghai 200433 China.

Abstract

Terahertz (THz) photon detection is of particular appealing for myriad applications, but it still lags behind efficient manipulation with electronics and photonics due to the lack of a suitable principle satisfying both high sensitivity and fast response at room temperature. Here, a new strategy is proposed to overcome these limitations by exploring the photothermoelectric (PTE) effect in an ultrashort (down to 30 nm) channel with black phosphorus as a photoactive material. The preferential flow of hot carriers is enabled by the asymmetric Cr/Au and Ti/Au metallization with the titled-angle evaporation technique. Most intriguingly, orders of magnitude field-enhancement beyond the skin-depth limit and photon absorption across a broadband frequency can be achieved. The PTE detector has excellent sensitivity of 297 V W^-1, noise equivalent power less than 58 pW/Hz^0.5, and response time below 0.8 ms, which is superior to other thermal-based detectors at room temperature. A rigorous comparison with existing THz detectors, together with verification by further optical-pumping and imaging experiments, substantiates the importance of the localized field effect in the skin-depth limit. The results allow solid understanding on the role of PTE effect played in the THz photoresponse, opening up new opportunities for developing highly sensitive THz detectors for addressing targeted applications.

Keywords: black phosphorus; imaging; photothermoelectric effect; terahertz detectors.