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

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/Hz0.5, 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.

Tunable Linearity of High‐Performance Vertical Dual‐Gate vdW Phototransistors

“…[ 12,13 ] The detected wavelength can be extended beyond the bandgap through thermal effects (photothermoelectric or bolometric effects) of 2D semiconductors, further sacrificing speed. [ 14,15 ]…”

“…[12,13] The detected wavelength can be extended beyond the bandgap through thermal effects (photothermoelectric or bolometric effects) of 2D semiconductors, further sacrificing speed. [14,15] In contrast to phototransistors, 2D photodiodes with a p-n junction or Schottky junction usually work faster because of the strong built-in electric field. [16][17][18][19] It can be predicted that the photoresponse of a typical 2D photodiode is linear due to the absence of photoconductive gain, and the dark current is very weak under reverse bias or even no bias (photovoltaic effect).…”

High‐Performance Phosphorene‐Based Transistors Using a Novel Exfoliation‐Free Direct Crystallization on Silicon Substrates

“…Meanwhile, different techniques have also been introduced to overcome the instability of phosphorene. [ 17 ] Apart from its prominent applications in the fabrication of p‐type channel field effect transistors, [ 18 ] great attention has been made toward the realization of different devices such as optoelectronics, [ 19 ] thermoelectric, [ 20 ] energy storage, [ 21 ] sensors, [ 22–24 ] and bioelectronics devices. [ 25 ]…”

Two-Dimensional Black Phosphorus Nanomaterials: Emerging Advances in Electrochemical Energy Storage Science

“…As been mentioned, BP exhibits tunable direct-bandgap feature [ 75 ]. By manipulating layer number, the absorption rate of electromagnetic wave significantly increases and the absorption wavelength can be broadened to the full range of absorption spectrum [ 24 , 25 , 61 , 76 ]. When number of layers is reduced to one, phosphorene shows a high absorption rate in the ultraviolet region [ 42 ].…”

“…In addition, 2D BP possesses a much larger specific surface area (~ 2630 m 2 g −1 ) than graphene due to the puckered structure and increased layer distance. Therefore, 2D BP has been intensively studied and widely applied in various fields, such as ultrafast laser [ 24 ], bio-photonics [ 25 ], energy storage devices [ 26 ], optoelectronics [ 27 ], solar cell [ 28 ], and nanosensors [ 29 ].…”