High‐Speed Graphene–Silicon–Graphene Waveguide PDs with High Photo‐to‐Dark‐Current Ratio and Large Linear Dynamic Range

Abstract

Abstract 2D materials (2DMs) meet the demand of broadband and low‐cost photodetection on silicon for many applications. Currently, it is still very challenging to realize excellent silicon‐2DM photodetectors (PDs). Here, graphene–silicon–graphene waveguide PDs operating at the wavelength bands of 1.55 and 2 µm, showing the potential for large‐scale integration, are demonstrated. For the fabricated PDs, the measured responsivities are ≈0.15 and ≈0.015 mA W −1 for the wavelengths of 1.55 and 1.96 µm, respectively. In particular, the PDs exhibit a high bandwidth of ≈30 GHz, an ultra‐low dark current of tens of pico‐amperes, a high normalized photo‐to‐dark‐current ratio of 1.63 × 10 6 W −1 , as well as a high linear dynamic range of 3 µW to 1.86 mW (and beyond) at 1.55 µm. According to the measurement results for the wavelength bands of 1.55/2.0 µm and the theoretical modeling for the silicon–graphene heterostructure, it is revealed that internal photoemission and photo‐assisted thermionic field emission dominantly contribute to the photoresponse in the graphene–silicon Schottky junctions under moderately high bias voltage, which helps the future work to further improve the performance.