Atomistic modeling of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="bold">a</mml:mi><mml:mo>+</mml:mo><mml:mi mathvariant="bold">c</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>-mixed dislocation core in wurtzite GaN

Belabbas, I.; Béré, A.; Chen, J.; Petit, Sébastien; Belkhir, M.A.; Ruterana, P.; Nouet, G.

doi:10.1103/physrevb.75.115201

Cited by 46 publications

(36 citation statements)

References 46 publications

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“…Theoretical predictions were also made using a Metropolis Monte Carlo method, with the positions of Ga and In atoms swapped at random within a cylindrical region of 4.46 nm around a dislocation core, and with differences in energies between trial configurations calculated by geometry optimization using the LAMMPS molecular dynamics code (MD) [30] and StillingerWeber potentials for InN [20] and GaN [31] Carlo simulations were continued until the total potential energy of the cell converged, and from this equilibrium core configurations were extracted. Further details of this model are available in our previous work [33].…”

Section: Methodsmentioning

confidence: 99%

“…GPA was performed on the boxed region in the STEM-HAADF image in Figure 5 Furthermore, the STEM-HAADF image of a TD in Sample C (which does not contain any In) also shows a higher contrast near the TD core (as seen in Figure 6 As the double 5/6-atom core [31] and the 7-and the 9-atom rings at both ends of a dissociated 7/4/8/4/9-atom core [34] have all been suggested to introduce deep states in the GaN band gap, the new core structures observed for (a+c)-type TDs in In x Ga 1-x N films are likely to introduce additional states in the In x Ga 1-x N band gap. Therefore, the electronic properties of dislocations in In x Ga 1-x N are likely to be different from those in GaN.…”

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confidence: 99%

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Dislocation core structures in (0001) InGaN

Rhode

Horton

Sahonta

et al. 2016

Journal of Applied Physics

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Abstract:Threading dislocation core structures in c-plane GaN and In x Ga 1-x N (0.057 ≤ x ≤ 0.20) films were investigated by aberration-corrected scanning transmission electron microscopy. a-type dislocations are unaffected by alloying with indium and have a 5/7-atom ring core structure in both GaN and In x Ga 1-x N. In contrast, the dissociation lengths of (a+c)-type dislocations are reduced and new 7/4/9-atom ring and 7/4/8/5-atom ring core structures were observed for the dissociated (a+c)-type dislocations in In x Ga 1-x N, which is associated with the segregation of indium near (a+c)-type and c-type dislocation cores in In x Ga 1-x N, consistent with predictions from atomistic Monte Carlo simulations.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Dislocation core structures in (0001) InGaN

Rhode

Horton

Sahonta

et al. 2016

Journal of Applied Physics

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“…Since it has been observed that the GaN surfaces do not exhibit Fermi-level pinning, they were postulated to lack mid-gap states [6,7]. However, first-principles calculations for numerous dislocations, including partial dislocations [8,9],threading edge [10,11], screw [12], and mixed [13,14] dislocations, have shown that these dislocations all have deep-level states. Hence, GaN may not be immune to nonradiative recombination of its free carriers at its dislocations.…”

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confidence: 99%

Kinetic path towards the passivation of threading dislocations in GaN by oxygen impurities

et al. 2017

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“…These potentials have previously been used with success to study dislocations in GaN 26,28,29 InN 30 and In x Ga 1-x N alloys 31 including quantum dot systems 32 35 . There are sometimes multiple atomic configurations possible at the core for each Burgers vector, and these are typically referred to by the number of atoms in the atomic rings that make up the core.…”

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confidence: 99%

“…In this work, the 5/7-atom ring atype core is favored since it is considered to be the most stable 9 , though other core types are considered, while the 5/7-atom ring (a+c)-type core is not studied since it has not been observed experimentally 16 and instead the 9/4/7-atom ring (a+c)-type core is favoured. Likewise, only the most stable c-type core 38 , and the double-5/6-atom ring a+c-type core 28 were studied.…”

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confidence: 99%

Segregation of In to Dislocations in InGaN

et al. 2015

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Dislocations are one-dimensional topological defects which occur frequently in functional thin film materials and which are known to degrade the performance of In x Ga 1-x N-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure re expected to occur in and around dislocation cores in In x Ga 1-x N alloy thin 2 films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films. KEYWORDSDislocations, III-nitrides, Monte Carlo, alloy segregation, atomistic modeling, STEM-EDX MAIN TEXTDislocations are ubiquitous one-dimensional topological defects that are found within thin films of nitride semiconductors, originating at the interface with the substrate, and threading up through the active region of the device before terminating at the crystal surface 1 . These dislocations can severely degrade device efficiencies 2 , and lifetimes 3 and are responsible for a broad range of undesirable behavior such as leakage currents 4 and properties such as reduced internal quantum efficiencies 5 and defect states 6,7,8,9,10 that can act as non-radiative recombination centers. In x Ga 1-x N-based alloy semiconductors are used in light-emitting diodes 11 , laser diodes 12 and solar cells 13 , which can be tuned to emit or absorb respectively over the entire visible spectrum by varying the In composition 14 . In x Ga 1-x N is subject to very high threading dislocation densities of up to 10 11 cm -2 and typically around 10 9 cm -2 when grown by metalorganic vapourphase epitaxy 15 (MOVPE), of which the majority have a-type ('edge') or (a+c)-type ('mixed') Burgers vectors with < 1% 16 being c-type ('screw'). High dislocation densities are associated with short lifetimes in InGaN-based optoelectronic devices 17 . The electronic properties of dislocations are determined by the local bonding in the region of the dislocation core 8 . It is therefore important to determine whether or not there are local differences in the alloy composition near dislocation cores in In x Ga 1-x N. Such composition fluctuations are likely to 3 affect the electronic properties of the dislocations and would therefore affect device performance.Each dislocation is associated with a strain field determined by its Burgers vector. Since the In atom is larger than the host Ga atom, it is expected that if the In atoms are sufficiently mobile during growth, then they will segregate to the tensile part of the dislocation strain field 18 .Previous theoretical work has shown that the extreme case of a pure InN c-type dislocation core in an In x Ga 1-x N alloy is more energetically favorable compared to the equivalent In x Ga 1-x N core 19 , and also that it is favorable for In atoms to bind to a c-type dislocation core in GaN 20 . Due to the sensitivity required to detect small variations in alloy concentration on sh...

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Atomistic modeling of the(a+c)-mixed dislocation core in wurtzite GaN

Cited by 46 publications

References 46 publications

Dislocation core structures in (0001) InGaN

Dislocation core structures in (0001) InGaN

Kinetic path towards the passivation of threading dislocations in GaN by oxygen impurities

Segregation of In to Dislocations in InGaN

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