Substrate effects on the speed limiting factor of WSe₂ photodetectors

Abstract

We investigate the time-resolved photoelectric response of WSe2 crystals on glass and flexible polyimide substrates to determine the effect of a changed dielectric environment on the speed of the photodetectors....

Pitfalls in Determining the Electrical Bandwidth of Nonideal Nanomaterials for Photodetection

“…The WSe 2 transition metal dichalcogenide detectors were prepared as reported elsewhere using Scotch tape exfoliation of TMDC flakes onto lithographically fabricated electrodes (WSe 2 : 2 nm Ti/10 nm Au, MoS 2 : 4 nm Ti/20 nm Au, 5 μm × 80 μm, finger width = 10 μm, flake thickness WSe 2 : 30 nm, flake thickness MoS 2 : 110 nm). In contrast, the MoS 2 detectors were fabricated by exfoliating the TMDC first before performing lithography onto the flakes.…”

Toward Gigahertz Photodetection with Transition Metal Dichalcogenides

“…21 For bulk WSe 2 , we found that the dielectric constant of the substrate alters not only the response time but also the speed- 3a). 3 For the detectors on glass, the response time is slower than the RC constant, presumably now limited due to drift limitation as a consequence of a shrunken depletion layer induced by the higher dielectric screening (Figure 3b). The maximal achieved bandwidth is 2.6 MHz.…”

“…Glass has a larger dielectric constant of 4.5–8, in comparison to the weaker screening on polyimide with 3.7. For polyimide, the WSe 2 detectors are faster and are limited by the RC time (Figure a) . For the detectors on glass, the response time is slower than the RC constant, presumably now limited due to drift limitation as a consequence of a shrunken depletion layer induced by the higher dielectric screening (Figure b).…”

“…The X -axes list all measured contacts with the respective channel length. Adapted with permission from ref . Copyright 2022 PCCP Owner Societies.…”

Edge contacts accelerate the response of MoS2 photodetectors

“…13 Many methods have been used in the search for ultrafast photodetectors based on nanomaterials: chemical doping, 14 heterojunction implementation, 15,16 photonic waveguide integration, 17 and small channel lengths, 18,19 to name a few. In addition, parameters such as the choice of substrate, 18,20 interface roughness, 21 electrode material, 10,22,23 and geometry 13,24,25 or environment 26,27 must be considered each time.…”