Infrared Photodetector Based on van der Waals MoS<sub>2</sub>/MoTe<sub>2</sub> Hetero‐Bilayer Modulated by Photogating
Bining Sheng, Jiong Yang, Chao Zhang, Maoxiang Jiang, Wentao Ma, Xiaoyi Liu, Kourosh Kalantar‐Zadeh, Zefeng Chen, Xiaofeng Li
Abstract
Abstract Photodetectors based on 2D hetero‐bilayers can overcome the bandgap limitations of individual 2D monolayers and operate at relatively long wavelengths. However, ultra‐low light absorptions within hetero‐bilayers result in extremely weak photoresponsivity. Here, an infrared photodetector based on the MoS 2 /MoTe 2 type‐II hetero‐bilayer is demonstrated to reach a photoresponsivity of 0.55 A W −1 at 1550 nm, well beyond energy band cut‐offs of monolayer MoS 2 and MoTe 2 , primarily resulted from the photogating effect. Raman and photoluminescence (PL) spectroscopy reveal strong interlayer couplings in the hetero‐bilayer, and a broad PL peak around 1550 nm is observed that is ascribed to interlayer transitions of carriers. The photodetector showcases a broadband detection capability from 1100 to 1700 nm, with a peak at 1550 nm corresponding to the interlayer absorption. Electrical characterization of the hetero‐bilayer‐based field‐effect transistor and kelvin probe force microscopy reveal efficient interlayer hole transfer. The highly responsive MoS 2 /MoTe 2 infrared photodetector offers a large photo‐gain of ≈10 3 and a time constant of 130 ms. The research illuminates how interlayer transitions affect 2D hetero‐bilayer‐based photodetectors and advances the utilization of layered semiconductor heterostructures.