Two-dimensional Si2Te2 monolayers and Si2Te2/Sb2Te3 van der Waals heterostructures: promising infrared photodetector materials

Abstract

Recently, the experimental realization of Si-based 2D materials such as Si₂Te₂ monolayers and Si₂Te₂/Sb₂Te₃ van der Waals (vdW) heterostructures has led to their practical applications in optoelectronic devices due to their narrow bandgaps, which are crucial for the infrared (IR) spectral range. Herein, the optoelectronic properties of Si₂Te₂ monolayers and Si₂Te₂/Sb₂Te₃ vdW heterostructures are investigated based on the framework of density functional theory calculations and nonequilibrium Green's function simulations. The stacking configurations, chemical bonding features and electronic structures of Si₂Te₂/Sb₂Te₃ vdW heterostructures are systematically unraveled. Moreover, the simulations of p–i–n junctions highlight that the Si₂Te₂ monolayer achieves its highest photoresponsivity of 0.64 A W⁻¹ in the mid-IR region, while maintaining a decent photocurrent density. It is interesting to note that the Si₂Te₂/Sb₂Te₃ vdW heterostructure based p–i–n junction reaches the distinguished highest photocurrent density of 27.33 A m⁻² and photoresponsivity of 1.24 A W⁻¹ in the near-IR region. This work is expected to provide valuable insights into designing high-performance IR photodetectors using Si₂Te₂-based 2D materials.