High-Bandwidth Zero-Biased Waveguide-Integrated p‑n Homojunction Graphene Photodetectors on Silicon for a Wavelength Band of 1.55 μm and Beyond

The p-n homojunction graphene photodetectors (GPDs) based on the photothermoelectric (PTE) effect have drawn much attention for featuring zero-bias operation (i.e., zero dark current) with a bandwidth of tens of GHz. However, most waveguide-integrated GPDs were demonstrated for the 1.55 μm wavelength band. Here, we realize high-performance silicon waveguide integrated GPDs enabling efficient light absorption at both wavelength bands of 1.55 and 2 μm. The broadband operation of the present PTE GPDs is analyzed theoretically and experimentally. When operating at 1.55 μm, the GPD typically exhibits a responsivity of ∼2.81 V/W and a 3 dB bandwidth of >40 GHz (setup-limited) under zero bias. When the GPDs operate at 2 μm under zero bias, the responsivity is about 2.78–4 V/W and the 3 dB bandwidth is >22 GHz (setup-limited). The measured linear dynamic range is over 24 dB for both wavelength bands of 1.55 and 2 μm. The present high-performance waveguide-integrated GPD provides a promising option for the applications of silicon photonics beyond 1.55 μm, such as optical communications, photonics sending, etc.