Investigation of the Crystallization Region for High-Quality GaN Growth in Na-Flux Method

The Na-flux method is recognized as a highly promising technique for growing large-size, high-quality gallium nitride (GaN) single crystals due to its relatively mild growth temperatures and pressures. However, precisely identifying and effectively regulating the critical crystallization regimes, which dictate crystal quality, remains a fundamental challenge for scalable and stable growth. This study employs a synergistic multiscale approach integrating macroscopic numerical analysis, molecular dynamics (MD) simulations, and reported experimental data-to systematically investigate the crystallization kinetics of GaN within 973-1173 K and 1-7 MPa. By establishing a comprehensive thermodynamic model based on dynamic supersaturation, a precise temperature-pressure (T-P) phase diagram was constructed, successfully delineating the high-quality epitaxial growth regions. The accuracy of these optimal windows was rigorously verified through MD simulations and literature-based experimental growth outcomes. This multiscale framework elucidates the synergistic regulation mechanisms of T and P from both macroscopic and atomistic perspectives, providing robust theoretical guidance for optimizing process parameters in the growth of high-quality GaN crystals.