The formation mechanism of voids in physical vapor deposited AlN epilayer during high temperature annealing

Abstract

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.