GeSn lateral p-i-n waveguide photodetectors for mid-infrared integrated photonics.

In this Letter, we demonstrate mid-infrared (MIR) lateral p-i-n GeSn waveguide photodetectors (WGPDs) on silicon, to the best of our knowledge for the first time, as a key enabler of MIR electronic-photonic integrated circuits (EPICs). Narrow-bandgap GeSn alloys were employed as the active material to enable efficient photodetection in the MIR region. A lateral p-i-n homojunction diode was designed and fabricated to significantly enhance the optical confinement factor of the guided modes and thus enhance the optical responsivity. Thus, a photodetection range of up to 1950 nm and a good responsivity of 0.292 A/W at 1800 nm were achieved. These results demonstrate the feasibility of planar GeSn WGPDs for monolithic MIR EPICs on silicon.