A Family of Two-Dimensional Quaternary Compounds ABXY (A = K, Na; B = Li, Na; X = Al, Ga, In; Y = P, As, Sb) for Optoelectronics Applications.

Expanding material types and developing two-dimensional (2D) semiconductor materials with high performance have been hotspots in the field. In this research, it is found that the 12 existing semiconductors ABXY (A = K, Na; B = Li, Na; X = Al, Ga, In; Y = P, As, Sb) have a pronounced layered structure. We predict their 2D structures and properties, using first-principles calculations. Lower exfoliation energies confirm the feasibility of mechanical exfoliation from their bulk phases and that the 2D structures can be stabilized independently at room temperature. Interestingly, ABXY has an anionic tetrahedral one-dimensional chain or two-dimensional mesh structure of [XY] composed of elements III-V. All ABXY monolayers exhibit direct or indirect band gap features (0.78-1.94 eV). More encouragingly, the ABXY monolayers possess ultrahigh carrier mobilities (∼10 cm V s) at room temperature. Furthermore, the results based on the nonequilibrium Green's function indicate that 2D ABXY exhibits a high ON/OFF ratio (∼10). To sum up, the ABXY family is an outstanding promising candidate for optoelectronics application.