The voids will be formed in the physical vapor deposited (PVD)-AlN epilayer after high temperature annealing. In this work, the formation mechanism of voids and its effect on crystal quality are investigated. Based on microstructural analysis and first principles calculations, it is confirmed that (1) the dislocations mainly gather around the voids and the strain status around the voids is similar to other regions in the same PVD-AlN epilayer, (2) the paired dislocations with opposite signs prefer to move closer and react with each other during high temperature annealing, thus contributing to the formation of voids, (3) the voids provide the inner surface for dislocations to terminate, decreasing the density of the threading dislocation propagating to the surface, and (4) the emergence of dislocations is energetically favorable and the energy dropped by 5.93 eV after the two isolated dislocation lines fused into a void by overcoming a barrier of 1.34 eV. The present work is of great significance for improving the quality and performance of AlN materials and devices.

中文翻译：

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高温退火物理气相沉积AlN外延层空洞形成机制

高温退火后，物理气相沉积 (PVD)-AlN 外延层中将形成空隙。在这项工作中，研究了空洞的形成机制及其对晶体质量的影响。基于显微结构分析和第一性原理计算，确定（1）位错主要聚集在空隙周围，空隙周围的应变状态与同一PVD-AlN外延层中的其他区域相似，（2）成对的位错与相反的符号在高温退火过程中更喜欢靠近并相互反应，从而有助于形成空隙，（3）空隙为位错终止提供了内表面，降低了传播到表面的穿透位错的密度，(4) 位错的出现在能量上是有利的，在两条孤立的位错线克服1.34 eV 的势垒融合成空隙后，能量下降了5.93 eV。目前的工作对于提高AlN材料和器件的质量和性能具有重要意义。