High-performance ultra-violet phototransistors based on CVT-grown high quality SnS2 flakes

Abstract

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 (R_λ ≈ 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.