High‐Speed and High‐Responsivity Hybrid Silicon/Black‐Phosphorus Waveguide Photodetectors at 2 µm

Abstract Silicon photonics is being extended from the near‐infrared window of 1.3–1.5 µm for optical fiber communications to the mid‐infrared (mid‐IR) wavelength‐band of 2 µm or longer for satisfying the increasing demands in many applications. Mid‐IR waveguide photodetectors on silicon have attracted intensive attention as one of the indispensable elements for various photonic systems. However, when combining traditional semiconductor materials with silicon, there are some challenges due to lattice mismatch and thermal expansion mismatch. As an alternative, two‐dimensional (2D) materials provide a new and promising option for enabling active photonic devices on silicon. Here black‐phosphorus (BP) thin films with optimized medium thicknesses (≈40 nm) are introduced as the active material for light absorption and silicon/BP hybrid ridge waveguide photodetectors at 2 µm are demonstrated with a high responsivity of 306.7 mA W −1 at a low bias voltage of 0.4 V. The 3 dB‐bandwidth is up to 1.33 GHz and an experiment of a 4.0 Gbit s −1 data receiving is also demonstrated.