The Role of Growth Conditions in Modulating Nitrogen Diffusion During Gallium Nitride Crystal Growth by Sodium Flux Method

This study investigates the mass and heat transport mechanisms in GaN crystal growth using the Na-flux method, focusing on how temperature, pressure, and temperature gradient affect nitrogen diffusion. Results indicate that increasing temperature enhances nitrogen concentration growth, while higher supersaturation at lower temperatures favors growth along the c-axis, forming a pyramidal morphology. Conversely, higher temperatures with lower supersaturation promote a step-flow growth mode, improving crystal quality. Although pressure has a lesser impact on nitrogen migration, it affects the growth rate and supersaturation, influencing crystal quality and morphology. A negative temperature gradient leads to spontaneous nucleation, causing polycrystalline structures. This research provides crucial insights into optimizing growth conditions for high-quality GaN single crystals, offering a theoretical basis and design guidelines to enhance growth rates and stability, with significant implications for crystal growth processes.