Novel Two-Dimensional Semiconductor SnP₃ with High Carrier Mobility, Good Light Absorption, and Strong Interlayer Quantum Confinement

We propose a novel two-dimensional (2D) SnP₃ crystal that possesses low indirect band gaps of 0.67 eV (monolayer) and 1.03 eV (bilayer) and high kinetic and thermal stability until 500 K. The 2D SnP₃ shows strong interlayer quantum confinement effects, resulting in a band gap increase from mono- to bilayer, and then a band gap decrease from bi- to triple layer leading to a semiconductor-metal transition. Monolayer SnP₃ has large hole mobility (992 cm² V^-1 s^-1), whereas bilayer SnP₃ has high electron mobility (8002 cm² V^-1 s^-1) which is comparable to that of phosphorene. The static dielectric constants of mono- and bilayer SnP₃ are 3.21 and 5.24, respectively. Both monolayer and bilayer SnP₃ show strong light absorption in the visible and ultraviolet regions. The indirect band gap of monolayer SnP₃ decreases under biaxial compressive strain and increases under biaxial tensile strain. Especially, when the biaxial compressive strain reaches to 6%, monolayer SnP₃ has a transition from semiconductor to metal. These results indicate that mono- and bilayer SnP₃ are promising novel 2D materials that have great potential applications in electronic and optoelectronic devices.