Enhanced Responsivity and Response Speed Modulation of Suspended WSe2 Photodetector

For 2-D materials, carrier trapping by interfacial traps/impurities is an important approach for enhanced photoconductive gain and responsivity, however, it is accompanied by a long response time. Here, we demonstrate a suspended multilayer WSe2 photodetector that balances responsivity and response speed. By using van der Waals (vdW) contacts, the suspended WSe2 photodetector has been built, and the device shows a good response in visible wavelengths. The responsivity can be up to 30.44 A/W at 20 nW and
${V}_{\text {GS}}$
= −60 V, which is higher than the substrate-supported photodetector. The improvement comes mainly from the effective weakening of the Schottky barrier by vdW contact. Moreover, the response speed can be tuned by the interfacial coupling effect (ICE) caused by gate voltage. The suspended WSe2 photodetector shows a rapid response of 0.23/0.1 s at
${V}_{\text {GS}}$
= 0 V, and the response time decreases to 30 ms at
${V}_{\text {GS}}$
= 20 V. The response speed remains at the same level as that of substrate-supported photodetector, owing to the reduction of SiO2 interface traps.