High-performance ultra-violet phototransistors based on CVT-grown high quality SnS2 flakes
van der Waals layered two-dimensional (2D) metal dichalcogenides, such as SnS2, have garnered great interest owing to their new physics in the ultrathin limit, and become potential candidates for the next-generation electronics and/or optoelectronics fields. Herein, we report high-performance UV photodetectors established on high quality SnS2 flakes and address the relatively lower photodetection capability of the thinner flakes via a compatible gate-controlling strategy. SnS2 flakes with different thicknesses were mechanically exfoliated from CVT-grown high-quality 2H-SnS2 single crystals. The photodetectors fabricated using SnS2 flakes reveal a desired response performance (Rλ ≈ 112 A W−1, EQE ≈ 3.7 × 104%, and D* ≈ 1.18 × 1011 Jones) under UV light with a very low power density (0.2 mW cm−2 @ 365 nm). Specifically, SnS2 flakes present a positive thickness-dependent photodetection behavior caused by the enhanced light absorption capacity of thicker samples. Fortunately, the responsivity of thin SnS2 flakes (e.g. ∼15 nm) could be indeed enhanced to ∼140 A W−1 under a gate bias of +20 V, reaching the performance level of thicker samples without gate bias (e.g. ∼144 A W−1 for a ∼60 nm flake). Our results offer an efficient way to choose 2D crystals with controllable thicknesses as optimal candidates for desirable optoelectronic devices.
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