Two-dimensional III-nitride alloys: electronic and chemical properties of monolayer Ga(1−x)AlxN

Abstract

Potential applications of III-nitrides have led to their monolayer allotropes, i.e., two-dimensional (2D) III-nitrides, having attracted much attention. Recently, alloying has been demonstrated as an effective method to control the properties of 2D materials. In this study, the stability, and the electronic and chemical properties of monolayer Ga_(1−x)Al_xN alloys were investigated employing density functional theory (DFT) calculations and the cluster expansion (CE) method. The results show that 2D Ga_(1−x)Al_xN alloys are thermodynamically stable and complete miscibility in the alloys can be achieved at ambient temperature (>85 K). By analyzing CE results, the atomic arrangement of 2D Ga_(1−x)Al_xN was revealed, showing that Ga/Al atoms tend to mix with the Al/Ga atoms in their next nearest site. The band gaps of Ga_(1−x)Al_xN random alloys can be tuned by varying the chemical composition, and the corresponding bowing parameter was calculated as −0.17 eV. Biaxial tensile strain was also found to change the band gap values of Ga_(1−x)Al_xN random alloys ascribed to its modifications to the CBM positions. The chemical properties of Ga_(1−x)Al_xN can also be significantly altered by strain, making them good candidates as photocatalysts for water splitting. The present study can play a crucial role in designing and optimizing 2D III-nitrides for next-generation electronics and photocatalysis.