Deciphering the stability of two-dimensional III-V semiconductors: Building blocks and their versatile assembly

Two-dimensionalization unlocks the unique and superior physical properties of materials, but extending it to nonlayered crystals is challenging. Using density functional theory and machine learning, we unveil a universal rule for creating stable two-dimensional counterparts of traditional high-performance III-V semiconductors, i.e., the versatile assembly of building blocks originating from orbital hybridization and electron transfers adhering to the electron counting rule. Akin to LEGO construction, the various building blocks are arranged in different configurations, introducing diverse two-dimensional structures with higher energetic stability than previous structures. Regression analysis reveals the energies of these structures as a linear superposition of the energies of their building blocks, further confirming the LEGO concept. Notably, the predicted two-dimensional GaSb exhibits a hole mobility (~10⁸ square centimeters per volt per second) that far surpasses that of graphene (2 × 10⁵ square centimeters per volt per second). This study highlights the expansion of nonlayered materials into two dimensions and the potential of two-dimensional confinement in traditional materials.