Suitable AlN Source Shape for Optimizing Gas Mass Transfer During AlN Crystal Growth

The optimization of the gas mass transfer route is particularly critical for the growth of aluminum nitride (AlN) crystals by the physical vapor transport method. With the influence of Steven’s flow and natural convection, the Al vapor returns to the AlN source surface or the low-temperature zone at the wall of the crucible for deposition, which not only affects the subsequent transmission of Al vapor but also the polycrystalline deposition layer is difficult to clean. Therefore, this work investigates the influence of AlN source surface shape for Al vapor transfer efficiency and analyzes the reasons for three AlN source surface shapes leading to different transport paths within the crucible. It is found that the convex surface is favorable for the optimization of Al vapor transport, which can significantly increase the growth rate of the AlN crystal. The growth zone on the convex surface has a higher temperature under the same conditions, and the dislocation density of the AlN crystals appears to be significantly reduced; the growth modes on both convex and concave surfaces have been improved. This work provides a new direction for the quality optimization and expansion growth of AlN crystals.