High-sensitive phototransistor based on vertical HfSe ₂/MoS ₂ heterostructure with broad-spectral response

Van der Waals heterostructures based on the two-dimensional (2D) semiconductor materials have attracted increasing attention due to their attractive properties. In this work, we demonstrate a high-sensitive back-gated phototransistor based on the vertical HfSe ₂/MoS ₂ heterostructure with a broad-spectral response from near-ultraviolet to near-infrared and an efficient gate tunability for photoresponse. Under bias, the phototransistor exhibits high responsivity of up to 1.42×10 ³ A/W, and ultrahigh specific detectivity of up to 1.39×10 ¹⁵ cm⋅Hz ^1/2⋅W ⁻¹. Moreover, it can also operate under zero bias with remarkable responsivity of 10.2 A/W, relatively high specific detectivity of 1.43×10 ¹⁴ cm⋅Hz ^1/2⋅W ⁻¹, ultralow dark current of 1.22 fA, and high on/off ratio of above 10 ⁵. These results should be attributed to the fact that the vertical HfSe ₂/MoS ₂ heterostructure not only improves the broadband photoresponse of the phototransistor but also greatly enhances its sensitivity. Therefore, the heterostructure provides a promising candidate for next generation high performance phototransistors.