[1100]/(1102) Twin boundaries in Wurtzite ZnO and Group-III-nitrates

The atomic structure and electronic effects of the [1100]/(1102) twin boundary in ZnO are studied using the combination of high-resolution Z-contrast imaging, first-principles density-functional total-energy calculations, and image simulations. The twin boundary is found to have the head-to-tail polarity configuration, which avoids dangling bonds, leading to a low twin-boundary energy of 0.040 J/m ². We further find that the same twin boundaries in wurtzite group-III-nitrides adopt the same structure, but the twin-boundary energies, 0.109 J/m ² in AlN, 0.107 J/m ² in GaN, and 0.051 J/m ² in InN, are higher than in ZnO. Investigations of the electronic structure reveal that the twin boundary does not introduce localized energy states in the band gap in either ZnO or the wurtzite group-III-nitrides.