Scaling thermodynamic model for the self-induced nucleation of GaN nanowires

Self-induced growth of nanowires is a fundamental phenomenon which is qualitatively different from the known growth mechanisms, such as the stress-driven formation of quantum dots or metal-catalyzed vapor-liquid-solid growth of nanowires. We present a scaling thermodynamic model that explains the self-induced nucleation of GaN nanowires by the anisotropy of surface energies coupled with the scaling growth anisotropy. The model shows why GaN tends to nucleate in the form of nanoislands rather than nanowires. It also elucidates the physical origin of the island-to-wire shape transformation at a certain critical radius. It is shown that the self-induced nanowire formation is sensitive to the sidewall surface energy that should be sufficiently low to favor growth anisotropy. The model is in a qualitative agreement with the experimental data and may be applied to other highly anisotropic growths driven by the surface energetics.