Defects in gallium nitride nanowires: First principles calculations

Atomic configurations and formation energies of native defects in an unsaturated GaN nanowire grown along the [001] direction and with (100) lateral facets are studied using large-scale ab initio calculation. Cation and anion vacancies, antisites, and interstitials in the neutral charge state are all considered. The configurations of these defects in the core region and outermost surface region of the nanowire are different. The atomic configurations of the defects in the core region are same as those in the bulk GaN, and the formation energy is large. The defects at the surface show different atomic configurations with low formation energy. Starting from a Ga vacancy at the edge of the side plane of the nanowire, a N-N split interstitial is formed after relaxation. As a N site is replaced by a Ga atom in the suboutermost layer, the Ga atom will be expelled out of the outermost layers and leaves a vacancy at the original N site. The Ga interstitial at the outmost surface will diffuse out by interstitialcy mechanism. For all the tested cases N-N split interstitials are easily formed with low formation energy in the nanowires, indicating N-2 molecular will appear in the GaN nanowire, which agrees well with experimental findings.

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Z. Wang was financially supported by the National Natural Science Foundation of China (Grant No. 10704014), the Young Scientists Foundation of Sichuan (Grant No. 09ZQ026-029), and UESTC (Grant No. JX0731). J. Li gratefully acknowledges financial support from the "One-Hundred Talents Plan" of the Chinese Academy of Sciences. F. Gao and W. J. Weber were supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC05-76RL01830.

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Z. Wang was financially supported by the National Natural Science Foundation of China (Grant No. 10704014), the Young Scientists Foundation of Sichuan (Grant No. 09ZQ026-029), and UESTC (Grant No. JX0731). J. Li gratefully acknowledges financial support from the "One-Hundred Talents Plan" of the Chinese Academy of Sciences. F. Gao and W. J. Weber were supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC05-76RL01830.