Atomic distribution in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">In</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">Ga</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">N</mml:mi></mml:mrow></mml:math>single quantum wells studied by extended x-ray absorption fine structure

Miyanaga, Takafumi; Azuhata, T.; Matsuda, Shigenobu; Ishikawa, Yoshikazu; Sasaki, Susumu; Uruga, Tomoya; Tanida, Hajime; Chichibu, S. F.; Sota, Takayuki

doi:10.1103/physrevb.76.035314

Cited by 20 publications

(29 citation statements)

References 16 publications

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“…This work is somewhat difficult to analyze in terms of the basic materials factors discussed above, due to the lack of information about the layer thicknesses. The results of Miyanaga et al [87] used EXAFS to study the In atom distribution in SQW structures, typical of those used in InGaN blue, green, and amber LEDs with x In values of 0.145, 0.2, and 0.275, respectively. Their results indicate that the atomic distribution is random in the horizontal direction, but with In-rich aggregates in the vertical direction.…”

Section: X-ray Fine Structure (Exafs)mentioning

confidence: 99%

Microstructures produced during the epitaxial growth of InGaN alloys

Stringfellow¹

2010

Journal of Crystal Growth

159

123

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Section: X-ray Fine Structure (Exafs)mentioning

confidence: 99%

Microstructures produced during the epitaxial growth of InGaN alloys

Stringfellow¹

2010

Journal of Crystal Growth

159

123

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“…1,2 The atomic microstructure of alloys is rarely perfectly random, instead exhibiting differently shaped precipitates, clusters, zigzag chains, and manifesting some degree of short-range order ͑SRO͒ and sometimes long-range order ͑LRO͒. 2 While it is expected that such microstructural features will affect the electronic structures, including carrier localization [3][4][5][6][7][8][9][10][11] and band gaps, 8,[12][13][14][15] theoretical studies have, until now, been restricted to investigate either perfectly random alloys ͑SRO= 0; LRO= 0͒ ͑Refs. 16-18͒ or "guessed," nonrandom microstructural features.…”

Section: Introductionmentioning

confidence: 99%

Bridging the gap between atomic microstructure and electronic properties of alloys: The case of (In,Ga)N

2010

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The atomic microstructure of alloys is rarely perfectly random, instead exhibiting differently shaped precipitates, clusters, zigzag chains, etc. While it is expected that such microstructural features will affect the electronic structures ͑carrier localization and band gaps͒, theoretical studies have, until now, been restricted to investigate either perfectly random or artificial "guessed" microstructural features. In this paper, we simulate the alloy microstructures in thermodynamic equilibrium using the static Monte Carlo method and study their electronic structures explicitly using a pseudopotential supercell approach. In this way, we can bridge atomic microstructures with their electronic properties. We derive the atomic microstructures of InGaN using ͑i͒ density-functional theory total energies of ϳ50 ordered structures to construct a ͑ii͒ multibody cluster expansion, including strain effects to which we have applied ͑iii͒ static Monte Carlo simulations of systems consisting of over 27000 atoms to determine the equilibrium atomic microstructures. We study two types of alloy thermodynamic behavior: ͑a͒ under lattice incoherent conditions, the formation enthalpies are positive and thus the alloy system phase-separates below the miscibility-gap temperature T MG , ͑b͒ under lattice coherent conditions, the formation enthalpies can be negative and thus the alloy system exhibits ordering tendency. The microstructure is analyzed in terms of structural motifs ͑e.g., zigzag chains and In n Ga 4−n N tetrahedral clusters͒. The corresponding electronic structure, calculated with the empirical pseudopotentials method, is analyzed in terms of band-edge energies and wave-function localization. We find that the disordered alloys have no electronic localization but significant hole localization, while below the miscibility gap under the incoherent conditions, In-rich precipitates lead to strong electron and hole localization and a reduction in the band gap.

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“…In this paper, we discuss the local structure around In atoms of In x Ga 1-x N multi-quantum-wells (MQW), where the samples are set to horizontal and vertical to the X-ray polarization electric vector. The results are discussed and compared with results of a previous SQW study [2].…”

Section: Introductionmentioning

confidence: 87%

“…Mole fluctuations of In atoms in In x Ga 1-x N active layers is proposed as the origin [1]. The local structure around In atoms in the single-quantum-well (SQW) In x Ga 1-x N (x=0.145, 0.20, 0.275) were studied by EXAFS [2]: In atoms are aggregated and located at the top and bottom in the vertical direction of the SQW plane. The In-In in-plane distance is smaller than that out-of-plane.…”

Section: Introductionmentioning

confidence: 99%

Local Structure around In Atoms in InxGa1−xN Multi-Quantum-Wells Studied by XAFS

Sasaki

Miyanaga

Azuhata

et al. 2007

AIP Conference Proceedings

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Indium K-edge EXAFS measurements were carried out to study local structures around In atoms in In x Ga 1-x N multi-quantum-well (MQW) structures of 10 periods with In 0.2 Ga 0.8 N (2.5 nm) and In 0.05 Ga 0.95 N (7.5 nm). We found the following: (1) Debye-Waller factors for In-In and In-Ga atomic pairs in MQW are smaller than those in single QW (SQW) In x Ga 1-x N. (2) The differences in the interatomic distances of In-In and In-Ga between the horizontal and vertical direction are small. These results indicate that the strain in the In x Ga 1-x N layer is reduced in MQW in comparison to SQW. (3) In atoms are randomly distributed in both the horizontal and vertical directions of the sample.

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Atomic distribution inInxGa1−xNsingle quantum wells studied by extended x-ray absorption fine structure

Cited by 20 publications

References 16 publications

Microstructures produced during the epitaxial growth of InGaN alloys

Microstructures produced during the epitaxial growth of InGaN alloys

Bridging the gap between atomic microstructure and electronic properties of alloys: The case of (In,Ga)N

Local Structure around In Atoms in InxGa1−xN Multi-Quantum-Wells Studied by XAFS

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