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

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 mu m, showing the potential for large-scale integration, are demonstrated. For the fabricated PDs, the measured responsivities are approximate to 0.15 and approximate to 0.015 mA W-1 for the wavelengths of 1.55 and 1.96 mu m, respectively. In particular, the PDs exhibit a high bandwidth of approximate to 30 GHz, an ultra-low dark current of tens of pico-amperes, a high normalized photo-to-dark-current ratio of 1.63 x 10(6) W-1, as well as a high linear dynamic range of 3 mu W to 1.86 mW (and beyond) at 1.55 mu m. According to the measurement results for the wavelength bands of 1.55/2.0 mu m 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.

Automated summary

Graphene-silicon-graphene waveguide photodetectors operating at wavelengths of 1.55 and 2 μm are demonstrated with potential for large-scale integration. The photodetectors exhibit high bandwidth, ultra-low dark current, high photo-to-dark current ratio, and high linear dynamic range.