The role of solid-melt interfaces in self-catalyzed growth kinetics of III-nitride semiconductors

Solid-melt interfaces govern metal-mediated epitaxy of gallium nitride (GaN) and related III-nitride semiconductors, yet a quantitative connection between interfacial structure and growth kinetics has remained elusive. Using atomistic simulations based on machine-learning interatomic potentials, we show that crystal orientation determines the local atomic arrangement and electrostatic character at the interface, inducing facet-dependent ordering in the adjacent melt. This ordering reshapes the N-transport free-energy landscape, substantially lowering migration barriers relative to pristine surfaces. Kinetic Monte Carlo simulations reveal that under realistic Ga-mediated molecular beam epitaxy (MBE) conditions, GaN grows in a diffusion-controlled, layer-by-layer regime, where the interface-normal adsorption free-energy landscape sets the dominant kinetic resistance. Combining facet-specific free-energy profiles with N diffusivity and solubility in liquid Ga, we develop a fitting-free model predicting growth rates of 0.01–0.04 nm/s, consistent with MBE-grown GaN nanoparticles. Similar ordering in other III-nitride systems indicates a generalizable route from atomistic energetics to anisotropic crystal growth kinetics.