Suitable AlN Source\nShape for Optimizing Gas Mass\nTransfer During AlN Crystal Growth

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