High-carrier mobility screening of polar multivalley two-dimensional alkaline earth monohalides

High carrier mobility in two-dimensional (2D) semiconductors is critical for next-generation electronics, yet identifying promising candidates remains challenging owing to multiple competing scattering mechanisms and the substantial computational expense of rigorous transport evaluation. Here, we generalize a symmetry-restoring deformation potential approximation formalism by accounting for multivalley degeneracy and present a hierarchical screening workflow integrating this formalism with rigorous Wannier-interpolated ab initio electron–phonon coupling calculations to accurately evaluate 2D materials for superior transport. Applying this screening workflow to the alkaline-earth metal monohalide family, the deformation-potential-approximation approach initially identifies these halides as promising candidates with optimistic mobility upper bounds of 102–104 cm2 V−1 s−1. Advancing rigorous electron–phonon coupling calculations to capture the decisive limiting role of polar optical phonons, we highlight monolayers CaI (μe≈180, μh≈93 cm2 V−1 s−1) and SrI (μe≈270, μh≈149 cm2 V−1 s−1) as robust candidates. This resilience is attributed to a synergistic interplay of small effective mass and large dielectric screening. This work establishes a reproducible framework for the precise evaluation of polar 2D semiconductors.