MoSe₂/WS₂ heterojunction photodiode integrated with a silicon nitride waveguide for near infrared light detection with high responsivity

We demonstrate experimentally the realization and the characterization of a chip-scale integrated photodetector for the near-infrared spectral regime based on the integration of a MoSe₂/WS₂ heterojunction on top of a silicon nitride waveguide. This configuration achieves high responsivity of ~1 A W⁻¹ at the wavelength of 780 nm (indicating an internal gain mechanism) while suppressing the dark current to the level of ~50 pA, much lower as compared to a reference sample of just MoSe₂ without WS₂. We have measured the power spectral density of the dark current to be as low as ~1 × 10⁻¹² A Hz^−0.5, from which we extract the noise equivalent power (NEP) to be ~1 × 10⁻¹² W Hz^−0.5. To demonstrate the usefulness of the device, we use it for the characterization of the transfer function of a microring resonator that is integrated on the same chip as the photodetector. The ability to integrate local photodetectors on a chip and to operate such devices with high performance at the near-infrared regime is expected to play a critical role in future integrated devices in the field of optical communications, quantum photonics, biochemical sensing, and more.