Interface structure and deformation mechanisms of AlN/GaN multilayers

Experimental results show that nano-ceramic/ceramic multilayers have excellent properties, and the deformation mechanisms need further investigation. In this work, molecular dynamics simulations were performed to study the interface structure of an AlN/GaN multilayer as well as the deformation mechanisms under uniform tensile/compressive loadings. After relaxation, a hexagonal misfit dislocation structure was observed at the interface. Analysis revealed that the misfit dislocation lines, surrounded by coherent regions, are of edge type. Unlike metal/metal multilayers and metal/ceramic multilayers, the stress-strain curve of the AlN/GaN multilayer subjected to in-plane loading shows only single main yield point. This is because that dislocations nucleate from the interface and emit into both layers almost simultaneously. A rhombus network was observed in GaN layer, attributed to the slip of dislocations along [112‾0](11‾00) and [21‾1‾0](011‾0) in wurtzite lattice structure. The tension-compression asymmetry was also found in the AlN/GaN multilayer.