CaP3: A New Two-Dimensional Functional Material with Desirable Band Gap and Ultrahigh Carrier Mobility

Two-dimensional (2D) semiconductors with direct and modest band gap and ultrahigh carrier mobility are highly desired functional materials for nanoelectronic applications. Herein, we predict that monolayer CaP 3 is a new 2D functional material that possesses not only a direct band gap of 1.15 eV (based on HSE06 computation) but also a very high electron mobility up to 19 930 cm 2 V –1 s –1, comparable to that of monolayer phosphorene. More remarkably, contrary to bilayer phosphorene which possesses dramatically reduced carrier mobility compared to its monolayer counterpart, CaP 3 bilayer possesses even higher electron mobility (22 380 cm 2 V –1 s –1 ) than its monolayer counterpart. The band gap of 2D CaP 3 can be tuned over a wide range from 1.15 to 0.37 eV (HSE06 values) through controlling the number of stacked CaP 3 layers. Besides novel electronic properties, 2D CaP 3 also exhibits optical absorption over the entire visible-light range. The combined novel electronic, charge mobility, and optical properties render 2D CaP 3 an exciting functional material for future nanoelectronic and optoelectronic applications.