Multiscale phase-field modeling of atomic layer deposition growth in hexagonal GaN based on first-principles surface energetics

We present a multiscale phase-field framework to simulate wurtzite GaN growth via atomic layer deposition, incorporating orientation-dependent surface energies from density functional theory. Energies of eight representative crystallographic orientations are fitted into a gradient energy formulation for the hexagonal lattice, ensuring symmetry compliance and numerical stability through an interface normal representation. Two- and three-dimensional simulations validate the approach: isotropic conditions yield symmetric growth, while anisotropy reproduces facet selection and orientation-dependent growth rates consistent with first-principles calculations. Simulations of trench structures under experimental atomic layer deposition (ALD) conditions demonstrate uniform sidewall coverage and effective trench filling, agreeing with observations. This work establishes a direct link between atomistic surface energetics and mesoscale morphology evolution, providing a general framework for modeling anisotropic thin-film growth of hexagonal materials in complex device geometries.