Unveiling the effect of crystal orientation on gallium nitride cutting through MD simulation

Gallium nitride (GaN) is a hard and brittle single crystal and shaping it into thin substrates for semiconductor applications is challenging. The quality of the machined surface can vary depending on the cutting orientation, primarily due to the hexagonal lattice structure of GaN. Therefore, understanding how crystallite orientation affects the cutting performance is crucial before developing a cost-effective machining process for GaN. This study used molecular dynamics (MD) simulation to investigate the cutting of GaN along different crystal orientations. Single grit cutting was performed to validate the simulation results. The simulation revealed distinct outcomes for different cutting directions. When cutting on a-plane or along the [-2110] direction on m-plane, removal efficiency was enhanced due to lower cutting resistance, and more dislocations were generated in the subsurface compared to other cutting directions. However, less phase transition and amorphization were induced, indicating lower energy consumption and smaller forces or stresses involved. Conversely, the cutting on c-plane or along the [0001] direction on m-plane showed the potential for achieving better surface integrity. This study provided valuable insights into the effect of crystallite orientation on the cutting performance of GaN and demonstrated that appropriate selection of cutting directions could result in improved surface quality, which are valuable for developing cost-effective machining technologies for GaN single crystals.