▎ 摘　　要

A nanophotonic photodetector is proposed with a multi-heterojunction structure based on silicon-ITO (Indium Tin Oxide) slot waveguide covered with 2D (two-dimensional) graphene sheets. A heavily n-doped ITO layer covers the whole device and works as an electrode to reduce the light loss at the metal-graphene interfaces. Different waveguides are arranged to design a one-dimensional photonic crystal (1D PhC) and the slot is defined by creating a defect in it. The PhC provides strong confinement of light, increasing the light-matter interaction, and thus generating more electron-hole (e-h) pairs or charge carriers under light illumination. Moreover, the multiple heterojunctions enhance the e-h generation and help enhancing the transportation of charge carriers. As a result, high photocurrent, fast response across a large bandwidth, strong electron-photon interaction, and also enhancement of photocarrier multiplications can be achieved. The photodetector realizes a photoresponsivity beyond 0.6 A/W at around 1550 nm wavelength. From 0.5 V-2 V of the bias voltage, the difference between the photocurrent and the dark current for the device with the PhC is more than 5 times that for the device without the PhC. Moreover, a 25 Gbit/s non-return to zero optical transmission is measured at 10 km transmission. The proposed device has diverse applications such as telecommunications, optical computing, interconnects, laser radar, lab-on-chip for sensing, and on-chip quantum photonics.