Low-Noise Te/MoTe₂ Heterojunction Waveguide-Integrated Photodetector

Two micrometer waveband has attracted much attention due to even-increasing data transmission and sensing needs. Waveguide-integrated photodetectors have been widely studied as one of the core devices in on-chip optical systems. However, bulk materials for photon-to-electron transition at 2 μm waveband such as HgCdTe or III–V compounds are incompatible with current integrated photonic platforms limited by lattice mismatch. As an alternative, van der Waals (vdW) materials, with exceptional optoelectronic characteristics, such as high mobility and strong light–matter interaction, can be freely integrated with arbitrary photonic platforms through vdW forces. In recent years, highly stable and narrow bandgap tellurium (Te) has been applied to construct mid-infrared detection with high responsivity and large bandwidth. However, the large shot noise of Te photodetectors results from a large dark current, limiting the detection of the weak light signals. Here, we introduce intrinsic n-type molybdenum ditelluride (MoTe2) to construct a PN heterojunction with Te, thereby dark current can be suppressed as a result of the depletion layer at the interface, which is the first time to integrate Te-based heterojunction on commercial silicon photonic platform above communication waveband. As a result, the detectivity of our device reaches 2 × 109 cm·Hz1/2·W–1. Simultaneously, the obtained waveguide-integrated Te/MoTe2 heterostructure photodetector possesses a responsivity of 94.16 mA·W–1 and a bandwidth of 36 MHz, benefiting from both evanescent wave enhancement and narrow channel for collection photoinduced carriers. The demonstrated waveguide-integrated Te/MoTe2 heterostructure photodetector is promising for applications in next-generation high-performance sensing and communication networks at 2 μm waveband.