Atomic structures and energies of partial dislocations in wurtzite GaN (original) (raw)
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9 SCIENTIFIC HIGHLIGHT OF THE MONTH Partial dislocations in wurtzite GaN
2000
The atomic structures and energies of 1=6 < 2023 > and 1=3 < 1010 > partial dislocations in wurtzite GaN are modelled using an empirical interatomic potential in combination with topological theory and anisotropic elasticity calculations. Twelve stable congurations of the 1=6 < 2023 > edge and mixed partial dislocations that bound I1 intrinsic basal stacking faults are obtained for
Atomistic Simulation of Undissociated 60° ; Basal Dislocation in Wurtzite GaN
Modeling and Numerical Simulation of Material Science, 2013
We have carried out computer atomistic simulations, based on an efficient density functional based tight binding method, to investigate the core configurations of the 60°basal dislocation in GaN wurtzite. Our energetic calculations, on the undissociated dislocation, demonstrate that the glide configuration with N polarity is the most energetically favorable over both the glide and the shuffle sets.
Electronic structure of 1/6〈2023〉 partial dislocations in wurtzite GaN
Journal of Applied Physics, 2011
The I 1 intrinsic basal stacking faults (BSFs) are acknowledged as the principal defects observed on f11 20g (a-plane) and f1 100g (m-plane) grown GaN. Their importance is established by recent experimental results, which correlate the partial dislocations (PDs) bounding I 1 BSFs to the luminescence characteristics of GaN. PDs are also found to play a critical role in the alleviation of misfit strain in hetero-epitaxially grown nonpolar and semipolar films. In the present study, the energetics and the electronic structure of twelve edge and mixed 1=6h20 23i PD configurations are investigated by first principles calculations. The specific PD cores of the dislocation loop bounding the I 1 BSF are identified for III-rich and N-rich growth conditions. The core structures of PDs induce multiple shallow and deep states, attributed to the low coordinated core atoms, indicating that the cores are electrically active. In contrast to edge type threading dislocations no strain induced states are found.
Partial dislocations in wurtzite GaN
Physica Status Solidi (a), 2005
The partial dislocations in wurtzite-structured GaN are reviewed and new results are presented. A multiplicity of partials is possible depending on stacking fault (SF) type, orientation, and interactions. The partials that delimit the I1 intrinsic basal SFs have 5/7, 8, or 12-atom cores as more probable configurations. The core structures of 90° partial dislocations with 1/6〈203〉 Burgers vector were studied from high resolution transmission electron microscopy observations in comparison with simulated models obtained from energetic calculations. Two cases were distinguished with one structure involving a 5/7 or 12-atom ring core and the other an 8-atom ring core. Another type of partials, in particular dislocations accommodating mirror variants of basal SFs were also studied experimentally. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomic core configurations of the -screw basal dislocation in wurtzite GaN
Journal of Crystal Growth, 2007
The results of atomistic calculations based on an ab initio tight-binding method are reported in this work for four configurations of the perfectã-screw basal dislocation in wurtzite GaN: pure shuffle, pure glide and two mixed shuffle-glide. Configurations with pure character (shuffle or glide) are found to be stable, whereas those with mixed shuffle-glide character are found to be transition-like configurations. Further, the calculations predict that the pure glide configuration, containing threefold coordinated atoms with an sp 2 hybridization, to be the most energetically favourable. r
Energetics of the 30 ∘ Shockley partial dislocation in wurtzite GaN
Superlattices and Microstructures, 2006
In the present work, we have investigated the relative energy of different core configurations of the 30∘ Shockley partial dislocation in wurtzite GaN. By using a modified Stillinger–Weber potential, we have carried out large scale calculations on models containing many thousands of atoms. Both glide and shuffle configurations have been considered within the two core polarities (Ga, N). Similarly to what was reported for conventional semiconductors, our calculations showed that the reconstructed glide configurations are energetically favoured over the shuffle ones.
Philosophical Magazine, 2006
Results obtained by atomic computer simulation based on an adapted Stillinger-Weber (S-W) potential concerning the structure and relative stability of lattice dislocations, tilt and twin boundaries in GaN are discussed. The method used for the search and description of all possible atomic configurations depends on the crystallographic structure; consequently it is of general application and the results are transferable to the wurtzite binary compounds. On the contrary, the relaxed structures and their relative energetic stability are potential dependent. 24/06/10 2 Contents 1 INTRODUCTION 2 COMPUTATIONAL METHOD 2.1 CONSTRUCTION OF SIMULATION CELLS 2.2 EMPIRICAL POTENTIAL DESCRIBING ATOMIC INTERACTIONS IN GAN 2.3 RELAXATION PROCEDURE 3 RESULTS 3.1 ATOMIC STRUCTURE AND ENERGY OF DISLOCATIONS 3.2 ATOMIC STRUCTURE AND ENERGY OF TILT BOUNDARIES 3.3 DISLOCATIONS MOBILITY AND BOUNDARY-DISLOCATION INTERACTION 3.4 ATOMIC STRUCTURE AND ENERGY OF TWIN BOUNDARIES
Ab-initio tight-binding study of the core structures of the c -edge dislocation in wurtzite GaN
physica status solidi (a), 2006
In the framework of ab-initio tight-binding methods, we modelled and studied the atomic and electronic core structures of the c-edge basal dislocation in wurtzite GaN. We found this dislocation to have four core configurations displaying 5/8/5-or 4/8-atom rings structures. All these configurations induce unfilled deep states in the top half of band gap.