Effect of Growth Domain Height on 4-Inch AlN Single Crystal Growth by PVT Method

As a pivotal strategic material enabling third-generation semiconductors, aluminum nitride remains plagued by formidable challenges in the fabrication of large-size single crystals, where the growth domain height emerges as a dominant constraint on the achievable crystal dimensions. This study systematically investigates the effects of four growth domain heights on AlN growth behavior, focusing on the thermal field distribution, mass transport, source porosity, vapor composition, and thermal stress evolution. Results indicate that the growth domain height significantly regulates the crucible thermal field, with axial temperature differences becoming more pronounced as the height increases. Under optimized conditions, the thermal field exhibited optimal uniformity, maintaining a suitable supersaturation near the nucleation site with stable mass transport. The aluminum partial pressure peaked in the nucleation zone, favoring directional deposition and crystal growth, while low von Mises stress helped suppress defect formation. Conversely, excessive growth heights induced reverse vapor transport, spontaneous source nucleation, and an inadequate supply to the nucleation site. A negative correlation between the AlN crystal density and aluminum partial pressure was observed, reflecting the coupling between source–vapor interactions and transport kinetics. Finally, 4-in. AlN single-crystal substrates were successfully fabricated. High-resolution X-ray diffraction showed full-width at half-maximum values of 195 and 208 arcseconds for the (002) and (102) rocking curves, respectively, indicating that crystal quality meets basic application requirements while still requiring improvement. This study elucidates the mechanism by which the growth domain height regulates AlN crystal growth, providing a theoretical foundation for preparing high-quality, large-size AlN single crystals.