Broad‐Spectrum Photodetection with High Sensitivity Via Avalanche Multiplication in WSe₂

Abstract High‐sensitivity broad‐spectrum photodetectors with detection capabilities ranging from ultraviolet to infrared have attracted significant attention for their application as photodetectors. They can be used as a receiver for all applications in optical communication for covering a wide spectral range with a single photodetector, which can significantly lower the overall system cost. In this study, by constructing an avalanche photodetector (APD) fabricated with 2D WSe₂, a high photoresponsivity of over 10⁷ A W⁻¹ for a broad spectrum of 405–1310 nm is achieved under an electric field higher than the critical field for the avalanche multiplication of 35 kV cm⁻¹, overcoming the limitation of the detectable wavelength induced by the energy bandgap of the material. The benchmark in terms of the photocurrent‐to‐dark current ratio and responsivity over a wide wavelength range demonstrates that the fabricated WSe₂ APD outperforms the reported 2D layered material‐based APDs and reported WSe₂ photodetectors. The obtained results can be attributed to the high‐gain mechanism via avalanche multiplication and phonon‐assisted photogeneration in WSe₂, enabling efficient photodetection beyond sub‐bandgap wavelengths. This result provides a promising general approach for developing a single photodetector that can cover a broad spectral range with a high sensitivity for future optical communication.