(a) Schematic of the silicon photonic-crystal (PhC) waveguide-integrated light-emitting diode and photodetector based on bilayer MoTe₂ p–n junction. (b) The schematic diagram of the device operating in LED mode and photodetector mode. The arrow indicates the direction of light propagation in the PhC waveguide. (c) EL emission intensity image at room temperature cover on top of a false-color optical image of the device. (d) The orange and green lines represent the transmission spectra of the waveguide before and after the bilayer MoTe₂ transfer, respectively. The normalized EL emission spectrum collected at the grating coupler represented by the blue line. (e) The temporal response of device in photodetector mode at zero bias. The response bandwidth of the device is 200 MHz. (f) The response spectrum of photodetector in the range from 1040 nm to 1240 nm, which shows the dependence of the responsivity on the wavelength due to photonic-crystal waveguide. Reproduced from Ref. [91] with permission from the Nature Publishing Group.