Deciphering the Stability of Two-Dimensional III-V Semiconductors—Building Blocks and Their Versatile Assembly

Two-dimensionalization unlocks the incredible potential of materials to exhibit unique and superior physical properties. Extending two-dimensionalization to non-layered crystalline materials presents both challenges and excitement. In this study, we employ high-throughput DFT calculation and machine learning to unveil a universal rule for creating stable two-dimensional counterparts of traditional high-performance III-V semiconductors: the versatile assembly of building blocks. The building blocks, comprising tetrahedrons, triangles, and distorted triangles, originate from the orbital hybridization and electron transfers, adhering to the Electron Counting Rule. By selecting and arranging various building blocks in different configurations, akin to assembling with LEGO, we successfully introduce a range of two-dimensional structures. These structures demonstrated superior energetic stability compared to theoretically predicted and experimentally synthesized counterparts. The tetrahedron building blocks contribute the most to stabilization, followed by triangular ones, as confirmed by linear regression analysis. The enhanced stability in these two-dimensional structures significantly reduces phonon scattering of carriers, leading to exceptional electronic properties. For instance, newly predicted two-dimensional GaSb exhibits remarkable hole mobility, approximately ∼10⁸ cm² V^-1s^-1, which surpasses the reported values for graphene (2 * 10⁵ cm² V^-1s^-1) and MoS₂(200 cm² V^-1s^-1). Our findings not only pave the way for expanding non-layered material systems into two-dimensional materials but also highlight the potential of two-dimensional confinement for these traditional materials.