MoS₂/Graphene Photodetector Array with Strain-Modulated Photoresponse up to the Near-Infrared Regime

MoS2, an emerging material in the field of optoelectronics, has attracted the attention of researchers owing to its high light absorption efficiency, even as an atomically thin layer. However, the covered spectra of the reported MoS2-based photodetectors are restricted to the visible range owing to their electronic bandgap (∼1.9 eV). Strain engineering, which modulates the bandgap of a semiconductor, can extend the application coverage of MoS2 to the infrared spectral range. The shrinkage of the bandgap because of the tensile strain on MoS2 enhances the photoresponsivity in the visible range and extends its sensing capability beyond its fundamental absorption limit. Herein, we report a graphene/MoS2/graphene metal-semiconductor-metal photodetector (PD) array with a strain-modulated photoresponse up to the spectral range of the near-infrared (NIR). The MoS2 PD array on a flexible substrate was stretched in the biaxial direction to a tensile strain level of 1.19% using a pneumatic bulging process. The MoS2-based line-scanning system was implemented by digitizing the output photocurrent of the strained MoS2 linear array with a low-noise complementary metal-oxide-semiconductor (CMOS) readout integrated circuit (IC) and successfully captured vis-NIR images in foggy conditions. Therefore, we extended the application of the MoS2 PD array to the NIR regime and demonstrated its use in real-life imaging systems.