Low-Noise Te/MoTe<sub>2</sub> Heterojunction Waveguide-Integrated\nPhotodetector

Two micrometer waveband has attracted much attention\ndue to even-increasing\ndata transmission and sensing needs. Waveguide-integrated photodetectors\nhave been widely studied as one of the core devices in on-chip optical\nsystems. However, bulk materials for photon-to-electron transition\nat 2 μm waveband such as HgCdTe or III–V compounds are\nincompatible with current integrated photonic platforms limited by\nlattice mismatch. As an alternative, van der Waals (vdW) materials,\nwith exceptional optoelectronic characteristics, such as high mobility\nand strong light–matter interaction, can be freely integrated\nwith arbitrary photonic platforms through vdW forces. In recent years,\nhighly stable and narrow bandgap tellurium (Te) has been applied to\nconstruct mid-infrared detection with high responsivity and large\nbandwidth. However, the large shot noise of Te photodetectors results\nfrom a large dark current, limiting the detection of the weak light\nsignals. Here, we introduce intrinsic n-type molybdenum ditelluride\n(MoTe<sub>2</sub>) to construct a PN heterojunction with Te, thereby\ndark current can be suppressed as a result of the depletion layer\nat the interface, which is the first time to integrate Te-based heterojunction\non commercial silicon photonic platform above communication waveband.\nAs a result, the detectivity of our device reaches 2 × 10<sup>9</sup> cm·Hz<sup>1/2</sup>·W<sup>–1</sup>. Simultaneously,\nthe obtained waveguide-integrated Te/MoTe<sub>2</sub> heterostructure\nphotodetector possesses a responsivity of 94.16 mA·W<sup>–1</sup> and a bandwidth of 36 MHz, benefiting from both evanescent wave\nenhancement and narrow channel for collection photoinduced carriers.\nThe demonstrated waveguide-integrated Te/MoTe<sub>2</sub> heterostructure\nphotodetector is promising for applications in next-generation high-performance\nsensing and communication networks at 2 μm waveband.