The diffusion of Ga in ZnO via interstitial-mediated mechanisms was investigated by first-principles calculations. Interstitial gallium was found to be thermally unstable and migrated easily into a neighbouring zinc lattice site with an approximately 0.5eV energy barrier, so the dominant interstitial-mediated mechanisms were the kick-out mechanisms rather than interstitial mechanisms. The energy barrier of gallium diffusion occurring via these kick-out mechanisms was 0.84 to 1.21eV.

First-Principles Study of the Diffusion of Ga via Interstitial-Mediated Mechanisms in ZnO. Huang, G.Y., Wang, C.Y., Wang, J.T.: Scripta Materialia, 2009, 61[3], 324-6