Enhanced responsivity and detectivity of fast WSe2 phototransistor using electrostatically tunable in-plane lateral p-n homojunction

Sayantan Ghosh, Abin Varghese, Kartikey Thakar, Sushovan Dhara and Saurabh Lodha ()
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Sayantan Ghosh: IIT Bombay
Abin Varghese: IIT Bombay
Kartikey Thakar: IIT Bombay
Sushovan Dhara: IIT Bombay
Saurabh Lodha: IIT Bombay

Nature Communications, 2021, vol. 12, issue 1, 1-9

Abstract: Abstract Layered transition metal dichalcogenides have shown tremendous potential for photodetection due to their non-zero direct bandgaps, high light absorption coefficients and carrier mobilities, and ability to form atomically sharp and defect-free heterointerfaces. A critical and fundamental bottleneck in the realization of high performance detectors is their trap-dependent photoresponse that trades off responsivity with speed. This work demonstrates a facile method of attenuating this trade-off by nearly 2x through integration of a lateral, in-plane, electrostatically tunable p-n homojunction with a conventional WSe2 phototransistor. The tunable p-n junction allows modulation of the photocarrier population and width of the conducting channel independently from the phototransistor. Increased illumination current with the lateral p-n junction helps achieve responsivity enhancement upto 2.4x at nearly the same switching speed (14–16 µs) over a wide range of laser power (300 pW–33 nW). The added benefit of reduced dark current enhances specific detectivity (D*) by nearly 25x to yield a maximum measured flicker noise-limited D* of 1.1×1012 Jones. High responsivity of 170 A/W at 300 pW laser power along with the ability to detect sub-1 pW laser switching are demonstrated.

Date: 2021
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DOI: 10.1038/s41467-021-23679-8

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