Enhanced responsivity of a graphene/Si-based heterostructure broadband photodetector by introducing a WS2 interfacial layer

Abstract

Photodetectors based on two-dimensional/three-dimensional (2D/3D) semiconducting heterostructures have attracted tremendous attention in recent years due to their novel performance. Here, we found that the photodetection performance of the graphene (Gr)/Si 2D/3D heterostructure can be very broadly enhanced by introducing an optimized ultrathin WS₂ film prepared by sulfidation as an interfacial layer. The fabricated Gr/WS₂(10.9 nm)/Si photodetector shows a wide spectralresponse from 400 to 1800 nm with a maximum photoresponsivity of 8.96 × 10⁴ A W⁻¹ and photodetectivity of 8.86 × 10¹¹ Jones at 690 nm, which are more than three orders of magnitude higher than that of the Gr/Si photodetector. Such a high photoresponsivity can be attributed to the strong photogain induced by the hole trap states that exist in the WS₂ film. With the increase in the WS₂ film thickness, the photoresponsivity increases firstly owing to the increase of hole trap states, and then decreases due to the decrease in light transmittance through WS₂. The device also shows a high responsivity of 0.735 A W⁻¹ at 1550 nm by forming type-II interlayer excitation. Our results indicate that 2D transition metal dichalcogenides (TMDCs) could be a good candidate functioning as an interfacial layer for high performance Gr/Si photodetectors, which provide a facile way for enhancing the photodetection performance of van der Waals 2D/3D heterostructure photodetectors.