The B3-GaN thin film was investigated by performing large-scale molecular dynamics (MD) simulation of nanoindentation. Its plastic behavior and the corresponding mechanism were studied. Based on the analysis on indentation curve, dislocation density, and orientation dependence, it was found that the indentation depths of inceptive plasticity on (001), (110), and (111) planes were consistent with the Schmid law. The microstructure evolutions during the nanoindentation under different conditions were focused, and two formation mechanisms of prismatic loop were proposed. The “lasso”-like mechanism was similar to that in the previous research, where a shear loop can translate into a prismatic loop by cross-slip; and the extended “lasso”-like mechanism was not found to be reported. Our simulation showed that the two screw components of a shear loop will glide on another loop until they encounter each other and eventually produce a prismatic dislocation loop.

The properties of ohmic contact and thermal boundary conductance between Al and GaN have been studied extensively, but the interface structures and deformation mechanisms in the Al/GaN multilayer can be rarely found in literatures. By molecular dynamics (MD) simulations, we systematically studied the interface structures and structural deformations in the Al/GaN multilayer. Two kinds of interface structures are identified according to the different terminal surfaces of GaN; glide-set terminal interface and shuffle-set terminal interface. Further analysis shows that interface has the maximum stress and misfit lines have the maximum stress values, which serve as the dislocation sources in the Al layer due to the larger stress in the interface. The mechanical responses of the Al/GaN multilayer exhibit a minor stage and some distinctive drops in the stress–strain curve. The first stage is associated with the dislocation nucleation from the interface. Upon further compression, more slip systems appear in the Al layer and dislocation nucleation in GaN could induce drops in curves. Meanwhile, the multiplications of dislocations cause strain hardening behaviours.