Semiconducting two-dimensional group VA-VA haeckelite compounds with superior carrier mobility

A series of two-dimensional (2D) single-layer binary group VA-VA crystals, where VA represents P, As, Sb and Bi, are explored by the first-principles calculations. Unlike the orthorhombic α-phase and hexagonal β-phase, these crystals have a tetragonal haeckelite lattice and are named as T-VA-VAs. These ultrathin 2D materials have high thermal stability and are semiconductors with moderate band gaps ranging from 0.80 to 2.68 eV (HSE06). The band gaps show a prevalent linear correlation with average ionization energies (AIEs) of different composites, and thus can be effectively designed. Furthermore, these materials exhibit superior carrier mobility, e.g. 2.96 × 10³ cm^-2 V^-1 s^-1 of T-SbBi, and considerable visible light absorption index. These novel 2D binary materials are expected to be fabricated and used as nanoelectronics and for solar energy harvesting.