Highly sensitive broadband terahertz modulator based on MAPbI<sub>3</sub>/Graphene/Si composite structure

Abstract

A high-performance silicon-based terahertz modulator is one of the key devices for building an ultrawideband terahertz-fiber hybrid communication system. In this paper, an ultrawideband terahertz modulator with large modulation depth based on a chalcogenide/graphene/silicon (MAPbI<sub>3</sub>/Graphene/Si) composite structure driven by near-infrared light (NIR) is proposed. The experimental results show that the graphene thin film and the chalcogenide hole transport layer can effectively promote the interfacial charge separation, increase the carrier complex lifetime, significantly enhance the surface conductivity of the device, further modulate the terahertz wave transmission amplitude, and realize the function of the light-controlled terahertz wave modulator under the NIR light drive. The terahertz transmission characteristics of the device are characterized by an 808 nm NIR modulation excitation source, and a large modulation depth of up to 88.3% is achieved in an ultra-wide frequency range of 0.2–2.5 THz and a low power density of 6.1 mW/mm<sup>2</sup> driven by NIR light, which is much higher than that of the bare silicon substrate (14.0%), with the significant advantages of high sensitivity, broadband, and large modulation depth. The corresponding semi-analytical device model is established and the experimental results are verified by simulation. The proposed MAPbI<sub>3</sub>/Graphene composite thin film is effective in enhancing the silicon-based modulator performance and provides a new strategy for the future integration of silicon-based terahertz modulators in NIR terahertz-fiber hybrid communication systems.