All‐Dielectric Nanostructure Fabry–Pérot‐Enhanced Mie Resonances Coupled with Photogain Modulation toward Ultrasensitive In₂S₃ Photodetector

Abstract As the fresh blood of 2D family, non‐layered 2D materials (2DNLMs) have demonstrated great potential in the application of next‐generation optoelectronic devices. However, stemming from the weak light absorption brought by atomically thin thickness and the interfacial recombination brought by surface dangling bonds, traditional 2DNLM photodetectors are always accompanied by limited performance. Herein, a structure that integrates Si nanopillar array and non‐layered 2D In₂S₃ to construct an ultrasensitive photodetector is designed. In particular, periodically Si nanopillars can act as Fabry–Pérot‐enhanced Mie resonators that can effectively control and enhance the light absorption of 2D In₂S₃. On the other hand, a vertical built‐in electric field is introduced in the In₂S₃ channel to capture photogenerated holes and leave electrons recycling in In₂S₃, obtaining a high photogain. Benefiting from these two mechanisms, this proposed photodetector presents a high responsivity of 4812 A W⁻¹ and short rise/decay time of 5.2/4.0 ms at the wavelength of 405 nm. Especially, a high light on–off ratio greater than 10⁶ and a record‐high detectivity of 5.4 × 10¹⁵ Jones are achieved, representing one of the most sensitive photodetectors based on 2D materials. This deliberate device design concept suggests an effective scheme to construct high‐performance 2DNLM optoelectronic devices.