Enhancing the photoresponse performance of graphene on silicon-based heterojunction as a broadband photodetector

Developing a high-performance photodetector based on graphene technology is a significant challenge in the field of light sensors. In this work, photodetectors based on a graphene monolayer/Si₃N₄/Si heterojunction connected to an Ohmic and a Schottky back junction have been realized. The current-voltage characteristics in dark and under illumination conditions in the range from UV to IR have been carried out. Estimation of the figures of merit has demonstrated that, compared to other Si-based devices such as Bi₂Te₃/Si, InSb/Si, Gr/SiO₂/Si and Gr/AlO₃/Si, the graphene/Si₃N₄/n-silicon heterojunction coupled with a Schottky contact exhibits the best performance in terms of rectifying behavior, low dark current, a responsivity higher than unity and the specific detectivity and Noise Equivalent Power of 3 × 10¹² Jones and 20 × 10^-14 W/Hz^1/2, respectively. Device performance has been studied by analyzing the electronic transport mechanisms involved, including the Thermionic, Ohmic, and Fowler-Nordheim mechanisms. Based on this approach, an estimation of the Schottky energy barrier of the graphene/Si₃N₄/n-silicon heterojunction reveals the tunability of the graphene Fermi level. The results demonstrate that this feature plays a crucial role in enhancing the photoresponse of graphene/n-Si-based devices, thereby facilitating the development of silicon technology for photodetection applications.