Effect of Exchange-Correlation Functionals on Schottky Barriers at Si/Metal Interfaces

Accurate prediction of Schottky barrier heights (SBHs) at metal-semiconductor interfaces is essential for understanding and optimizing charge injection in electronic and optoelectronic devices. However, first-principles calculations of SBHs remain challenging due to semiconductor bandgap underestimation, metal Fermi level placement, lattice mismatch, geometric alignment, and electrostatic potential alignment across the interfaces. In this work, we present a systematic and physically grounded assessment of computational strategies for SBH prediction using Si(111)/metal (Al, Cu, Ag, Au) interfaces as representative test cases. We evaluate multiple exchange-correlation treatments in combination with three distinct bulk reference protocols: relaxed, relaxed with spin-orbit coupling, and strained, consistent with the interface geometry. Benchmarking against experiment demonstrates that structural and electrostatic consistency between interface and bulk reference calculations is the dominant factor governing SBH accuracy. Mixed hybrid-semilocal approaches combined with strained reference protocols yield uniformly positive and significantly improved SBHs, achieving near-experimental accuracy with favorable computational cost and predictive performance.