Photoresponse-Bias Modulation of a High-Performance MoS Photodetector with a Unique Vertically Stacked 2H-MoS/1T@2H-MoS Structure.

Monolayer 2H-phase MoS-based photodetectors exhibit high photon absorption but suffer from low photoresponse, which severely limits their applications in optoelectronic fields. The metallic 1T phase of MoS, while transporting carriers faster, shows negligible response to visible light, which limits its usage in photodetectors. Herein, we propose an ultrafast-response MoS-based photodetector having a channel that consists of a 2H-MoS sensitizing monolayer on top of 1T@2H-MoS. The 1T@2H-MoS layer has a thickness of several nanometers and is a mixture of metallic 1T-MoS and semiconducting 2H-MoS, imparting metal-like properties to the photodetector. Compared with the monolayer 2H-MoS photodetector, we observed a drastic increase in the photoresponse of the 2H-MoS/1T@2H-MoS vertically stacked photodetector to a value of 1917 A W. Owing to the presence of metallic 1T-MoS within the metal-like 1T@2H-MoS, the performance of the 2H-MoS/1T@2H-MoS vertically stacked photodetector is voltage bias-modulated with an external quantum efficiency (EQE) of up to 448,384% and a specific detectivity of up to ∼10 Jones. The higher carrier density and higher mobility of the 1T@2H-MoS layer explain the better bias-modulated performance. In addition, the interface between 2H-MoS and 1T@2H-MoS ensures fewer dangling bonds and reduced lattice mismatching. Thus, this study presents an exclusive vertically stacked MoS-based photodetector that lays the foundation for the development of photodetectors exhibiting higher photoresponse.