Emerging two-dimensional group IV chalcogenides as building blocks for advanced infrared photodetectors

Abstract

The recent synthesis of a two-dimensional (2D) Te–Si–Si–Te monolayer with a four-atomic-layer-thick hexagonal lattice has attracted significant interest for its potential in infrared (IR) applications. In this regard, we conducted density functional theory calculations and non-equilibrium Green's function simulations to systematically explore the crystal structure, chemical bonds, and electronic and optical properties of the emerging 2D X–A–A′–X′ (X = Te, A = Si, A′ = Si, Ge, Sn, Pb and X′ = Se, Te), along with the optoelectronic performance of their corresponding vdW heterostructures. The electronic structures, chemical bonding and optical features of 2D X–A–A′–X′ were analyzed. Their indirect, narrow-bandgap semiconducting nature, obviously carrier mobility anisotropy and strong optical absorption were unraveled. Additionally, it was observed that the Te–Si–Pb–Te/Sb₂Te₃-, Te–Si–Si–Se/Sb₂Te₃-, and Te–Si–Ge–Se/Sb₂Te₃-based p–i–n junctions exhibited remarkably high photocurrent density and photoresponsivity in the IR region, underscoring their potential applications as IR photodetectors. Our work indicates that such emerging 2D group IV chalcogenides are potential building blocks for designing next-generation IR optoelectronic devices.