The manipulation of micro/nanostructures to customise their inherent material characteristics has garnered considerable attention. In this study, we present the selective activation of gallium arsenide (GaAs) via ultrafast laser-induced decomposition, which correlates with the emergence of ripples on the surface. This instigated a pronounced enrichment in the arsenic (As) concentration around the surface while inducing a depletion of gallium (Ga) at the structural depth. Theoretical simulations based on first principles exhibited a robust inclination towards the phase separation of GaAs, with the gasification of As-As pairs proving more facile than that of Ga-Ga pairs, particularly above the melting point of GaAs. As an illustrative application, a metal-semiconductor hybrid surface was confirmed, showing surface chemical bonding and surface-enhanced Raman scattering (SERS) through the reduction of silver ions on the laser-activated pattern. This laser-induced selective activation holds promise for broader applications, including the controlled growth of
ACCEPTED ARTICLE PREVIEWXu et al. Light: Advanced Manufacturing (XXXX)X: XXX 2 / 19 Pd and the development of Au/Ag alloy-based platforms, and thereby opens innovative avenues for advancements in semiconductors, solar cell technologies, precision sensing, and detection methodologies.