Nanoindentation-induced elastoplastic deformation mechanism in typical third-generation semiconductor materials SiC, AlN, and GaN

Third-generation wide-bandgap semiconductors (SiC, AlN, and GaN) are indispensable for high-temperature, high-power, and deep-ultraviolet optoelectronic devices, where their mechanical reliability directly determines the device lifetime. However, the atomic-scale elastoplastic deformation mechanisms, especially the crystallographic anisotropy and material-specific differences, remain poorly understood, severely hindering device design. This study employs both density functional theory (DFT) and molecular dynamics (MD) simulations to unravel the atomistic deformation mechanisms of SiC, AlN, and GaN under nanoindentation. Under c-plane indentation, perfect dislocation emission is constrained, the partial dislocation nucleation is triggered, and high-coordination phase transformations occur. Conversely, perfect dislocation is facilitated to slip on the m-plane. The critical stress for dislocation nucleation follows: SiC > AlN > GaN. The wurtzite symmetry dictates identical spatial atomic displacement pathways across the three materials, but their distinct intrinsic binding energies govern the displacement magnitudes. In addition, the critical stress required for perfect dislocation nucleation is consistently higher than that for partial dislocation nucleation, with SiC exhibiting a difference of 25% and GaN only 5%. The dislocation density of SiC is over 30% higher than that of AlN and GaN. Crucially, the dislocation loop mechanism is identified not merely as an intrinsic material trait, but as a gradient-driven topological response unique to nanoindentation. This work provides profound, mechanism-based guidelines for optimizing the mechanical reliability and orientation selection of next-generation wide-bandgap semiconductor devices.