High Photoresponsivity and Short Photoresponse Times in Few-Layered WSe₂ Transistors

Abstract

Here, we report the photoconducting response of field-effect transistors based on three atomic layers of chemical vapor transport grown WSe2 crystals mechanically exfoliated onto SiO2. We find that trilayered WSe2 field-effect transistors, built with the simplest possible architecture, can display high hole mobilities ranging from 350 cm(2)/(V s) at room temperature (saturating at a value of ∼500 cm(2)/(V s) below 50 K) displaying a strong photocurrent response, which leads to exceptionally high photoresponsivities up to 7 A/W under white light illumination of the entire channel for power densities p < 10(2) W/m(2). Under a fixed wavelength of λ = 532 nm and a laser spot size smaller than the conducting channel area, we extract photoresponsitivities approaching 100 mA/W with concomitantly high external quantum efficiencies up to ∼40% at room temperature. These values surpass values recently reported from more complex architectures, such as graphene and transition metal dichalcogenides based heterostructures. Also, trilayered WSe2 phototransistors display photoresponse times on the order of 10 μs. Our results indicate that the addition of a few atomic layers considerably decreases the photoresponse times, probably by minimizing the interaction with the substrates, while maintaining a very high photoresponsivity.

Fast High‐Responsivity Few‐Layer MoTe2 Photodetectors

“…[11,14,25] We used four-layer flakes for our photocurrent measurements as Pradhan et al showed that the use of few-layer TMDCs can reduce photocurrent response times while keeping photoresponsivity high. [26] Work done by Lezama et al also shows the transition of MoTe 2 to a direct band gap beginning at a flake thickness of four layers. [5] In Figure 1a, an optical microscopy image of a MoTe 2 flake of thickness from one to five layers is shown; the difference in flake thickness is…”

“…We believe that the fast photoresponse we observe is potentially due to three reasons: the thickness of our photodetectors, the crystal quality and the sampling rate/laser rise time used in our photoresponse measurements. We used four-layer flakes in our study, and other similar thickness TMDCs devices have previously shown a fast photoresponse [26,32] whereas using monolayer flakes appears to hamper the photoresponse speed (see Table S1 of the Supporting Information for full details of flake thickness in correlation to response speeds). We also note that for the fastest (to our knowledge) reported TMDC photoresponse time reported to date, for SnS 2 devices, [33] the crystal quality was shown to play a key role in determining the speed of response.…”

Broad Detection Range Rhenium Diselenide Photodetector Enhanced by (3‐Aminopropyl)Triethoxysilane and Triphenylphosphine Treatment

“…In particular, in the case of the ReSe 2 photodetector (Figure 3 h), a sharp increase or decrease was observed at the rising and decaying edges of the temporal photoresponse curves, indicating the much faster photoswitching speed of the ReSe 2 -based device compared to the MoS 2 device showing relatively slow changes. [ 53 ] Exceptionally, when a photodetector was fabricated on tin-based chalcogenides (SnS 2 or SnSe 2 ), its rising and decaying times were very short, as much as 5-7 µs. As expected, the ReSe 2 photodetector showed much shorter rising and decaying times compared to the MoS 2 photodetector ( τ r / τ d : 0.01/0.041 s for ReSe 2 and 6.97/12.2 s for MoS 2 ).…”

Mixed‐Dimensional 1D ZnO–2D WSe2 van der Waals Heterojunction Device for Photosensors

“…This approach using a 1D ZnO-2D WSe 2 heterojunction paves the way for the further development of electronic/optoelectronic applications using mixed-dimensional vdW heterostructures.transition metal dichalcogenides of MoS 2 , MoTe 2 , and WSe 2 , post-transition metal dichalcogenides of SnS 2 and SnSe 2 , and black phosphorus (BP), have been synthesized; furthermore, their prototype electronic/optoelectronic applications have been demonstrated for field-effect transistors, [3][4][5][6][7][8][9] logic circuits, [8,[10][11][12][13] light-emitting diodes, [14,15] phototransistors, [16][17][18][19][20] and photodiodes. In particular, the dangling-bond-free surface of 2D materials enables integration of differently dimensioned materials into mixed-dimensional vdW heterostructures.…”

“…To the best of our knowledge, this is the first demonstration of an optoelectronic device based on a 1D-2D hybrid vdW heterojunction. This approach using a 1D ZnO-2D WSe 2 heterojunction paves the way for the further development of electronic/optoelectronic applications using mixed-dimensional vdW heterostructures.transition metal dichalcogenides of MoS 2 , MoTe 2 , and WSe 2 , post-transition metal dichalcogenides of SnS 2 and SnSe 2 , and black phosphorus (BP), have been synthesized; furthermore, their prototype electronic/optoelectronic applications have been demonstrated for field-effect transistors, [3][4][5][6][7][8][9] logic circuits, [8,[10][11][12][13] light-emitting diodes, [14,15] phototransistors, [16][17][18][19][20] and photodiodes. [21][22][23][24] While there has been great progress in the field of 2D vdW materials, challenges have yet to be resolved for realizing their full potential:(1) implementation of high-speed operation to replace silicon or III-V compound semiconductors, (2) control of carrier type and concentration by doping, and (3) development of high quality all 2D vdW heterostructures over large areas.Recently, Jariwala et al introduced mixed-dimensional vdW heterostructures, which are a very promising strategy for overcoming the limitations of electronics based on 2D vdW materials.…”