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Lookup NU author(s): Professor Patrick Briddon
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Interatomic potential based molecular dynamics and ab initio calculations are employed to investigate the structural, thermal, and electronic properties of polar GaN/AlN core/shell nanowires. Nanowire models for the molecular dynamics simulations contain hundreds of thousands of atoms with different shell-to-nanowire ratios. The energetic and structural properties are evaluated through a detailed examination of the strain, the stress, and the displacement fields. It is found that the relaxation of the AlN shell is initiated at the edges, with the shell becoming increasingly stress free when the shell-to-nanowire ratio is increased. The basal lattice parameter a of the AlN shell is found to have a smaller value than the value predicted by the elasticity theory. The stresses on the GaN core are strongly influenced by the shell. The core retains the a lattice parameter of bulk GaN only up to a shell-to-nanowire ratio equal to 0.10 and is significantly compressed beyond this point. Concerning the thermal properties, the molecular dynamics simulations conclude that there is a linear relationship between the thermal conductivity and the shell-to-core area ratio of the GaN/AlN core/shell nanowires. The bandgaps of the nanowires are calculated through ab initio calculations of 10(3) atoms and the influence of the structural characteristics on the electronic properties is investigated. A well-defined relationship that predicts the bandgap of the GaN/AlN nanowires, follows the 2nd order Vegard's law and taking into account the shell-to-nanowire ratio, is established. Finally, the valence band maximum is found to be dominated by the surface N-2p levels, while the conduction band minimum is dominated by the core and interface Ga-3s, and the surface Al-2s levels. (C) 2016 AIP Publishing LLC.
Author(s): Pavloudis T, Termentzidis K, Komninou P, Latham CD, Briddon PR, Kioseoglou J
Publication type: Article
Publication status: Published
Journal: Journal of Applied Physics
Print publication date: 21/02/2016
Online publication date: 18/02/2016
Acceptance date: 01/02/2016
ISSN (print): 0021-8979
ISSN (electronic): 1089-7550
Publisher: American Institute of Physics
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