Impact of cation-based localized electronic states on the conduction and valence band structure of Al1−<i>x</i>In<i>x</i>N alloys

Schulz, Stefan; Miguel, A.; O’Reilly, Eoin P.

doi:10.1063/1.4872317

Cited by 22 publications

(19 citation statements)

References 38 publications

(50 reference statements)

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“…1). Our results support previous theoretical studies, which proposed In clustering as the cause of the unusually strong band gap bowing observed in In x Al 1-x N. [45][46][47][48] In our study of the oxygen impurity, we therefore adopt a structural model, in which the In atoms are clustered. To achieve a composition of x = 0.17, we considered a compact cluster of 8 In atoms in a 96-atom supercell.…”

supporting

confidence: 74%

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Meli

Miceli

Pasquarello

2017

Applied Physics Letters

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Using a hybrid density-functional scheme, we address the O impurity substitutional to N (O N ) in In 0.17 Al 0.83 N. Our modelling supports In clustering to account for the strong band-gap bowing observed in In x Al 1-x N alloys. To study the O N defect in In 0.17 Al 0.83 N alloys, we therefore consider a model containing an In cluster and find that the most stable configuration shows four In nearest neighbors. We show that such a O N defect forms a DX center and gives rise to two defect levels at 0.70 and 0.41 eV below the conduction band edge, in good agreement with experiment. The calculated defect energetics entail a fast nonradiative recombination upon photoexcitation at room temperature and account for the observation of persistent photoconductivity at low temperature.PACS numbers: 71.55. Eq,61.72.uj In the last decades, In x Al 1-x N has attracted a great deal of interest for its possible applications in electronic and optoelectronic devices. 1-3 In particular, In 0.17 Al 0.83 N is nearly lattice matched to GaN and can be used to realize strain-free heterostructures. 4,5 Applications include distributed Bragg reflectors, thick cladding layers in edge emitting lasers, waveguides exploiting the large difference in refractive indices between InAlN and GaN, and high-electron mobility transistors (HEMTs). [6][7][8] To control the electronic properties of these materials, it is important to understand the role of impurities. Upon growth through metalorganic vapor phase epitaxy (MOVPE), it is known that considerable concentrations of oxygen and carbon impurities are incorporated. 8 Experimental investigations have identified various defect states with activation energies ranging between 200 and 500 meV. 9-11 However, their origin has been difficult to ascertain and it has remained unclear whether these states relate to point defects or to dislocations. More recently, defect states have been measured at 68 meV and 270 meV and tentatively assigned to oxygen on the basis of their concentration. 12 The observation of persistent photoconductivity (PPC) effects has been taken as an indication supporting this interpretation, 12 as oxygen is known to give rise to DX centers in AlN. 13 In this Letter, we study the oxygen impurity substitutional to nitrogen (O N ) in In 0.17 Al 0.83 N through densityfunctional-theory calculations. We find that O N gives defect levels that are in agreement with experimental observations. These impurities behave like DX centers and can explain the origin of the persistent photoconductivity effects.In our calculations, we make use of the semilocal density functional introduced by Perdew, Burke, and Ernzerhof (PBE), 14 and of the hybrid functional introduced by Heyd, Scuseria, and Ernzerhof (HSE). 15,16 In the latter, the fraction of Fock exchange is set to α = 0.37 for AlN and to α = 0.19 for InN, in order to reproduce their experimental band gaps. For intermediate In x Al 1-x N alloys, the mixing coefficient α is linearly interpolated.We use normconserving pseudopotentials to treat corev...

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supporting

confidence: 74%

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Meli

Miceli

Pasquarello

2017

Applied Physics Letters

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“…When more than two In atoms share the same N atom in GaN, PR increases significantly at the VBE. However, these numbers are still significantly smaller than in In x Al 1−x N. 9 The CB remains delocalized even for four In atoms sharing the same N atom. To visualize the increase in PR, Fig.…”

Section: Resultsmentioning

confidence: 97%

“…It is important to note that these weak localization effects are in strong contrast to In x Al 1−x N alloys where already an isolated In atom introduces a strongly localized state in the CB. 9 This localized state in the CB hybridizes with the CBE, leading therefore to strong localization effects at the CBE. The differences in the basic physical properties, such as the band gap for example, are even more extreme between AlN and InN than they are between GaN and InN.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, we have shown for In x Al 1−x N alloys that LDA-DFT gives a good description of such effects in comparison with the computationally far more expensive hybrid functional approaches. 9 Therefore, LDA-DFT is a reasonable choice within the scope of the present study. The LDA-DFT is furthermore computationally much cheaper than a HSE framework and thus allows us to study larger systems, which then provide a better approximation of isolated In atoms in a larger GaN matrix.…”

Section: Density Functional Theory Calculationsmentioning

confidence: 99%

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Atomistic description of wave function localization effects in In_xGa_1-xN alloys and quantum wells

Schulz¹,

Marquardt

Coughlan

et al. 2015

SPIE Proceedings

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We present a detailed analysis of wave function localization effects in In x Ga 1−x N alloys and quantum wells. Our work is based on density functional theory to analyze the impact of isolated and clustered In atoms on the wave function localization characteristics in In x Ga 1−x N alloys. We address the electronic structure of In 0.25 Ga 0.25 N/GaN quantum wells by means of an atomistic tight-binding model. Random alloy fluctuations in the quantum well region and well-width fluctuations are explicitly taken into account. The tight-binding model includes strain and built-in field fluctuations arising from the random In distribution. Our density functional theory study reveals increasing hole wave function localization effects when an increasing number of In atoms share the same N atom. We find that these effects are less pronounced for the electrons. Our tight-binding analysis of In 0.25 Ga 0.75 N/GaN quantum wells also reflects this behavior, revealing strong hole localization effects arising from the random In atom distribution. We also show that the excited hole states are strongly localized over an energy range of approximately 50 meV from the top of the valence band. For the quantum wells considered here we observe that well-width fluctuations lead to electron wave function localization effects.

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“…We note that our conclusion does not contradict recent prediction of band perturbation by In-related electron and hole localized states. 50 Strikingly, g eq int values at 300 K of EXS peaks of pseudomorphic epilayers were as high 67% for x ¼ 0.14, 48% for x ¼ 0.23, and 44% for x ¼ 0.30. For example, CL spectra of the m-plane Al 0.86 In 0.14 N epilayer are shown as a function of temperature in Fig.…”

Section: B Optical Propertiesmentioning

confidence: 96%

High internal quantum efficiency ultraviolet to green luminescence peaks from pseudomorphic m-plane Al1−xInxN epilayers grown on a low defect density m-plane freestanding GaN substrate

Chichibu

Hazu

Furusawa

et al. 2014

Journal of Applied Physics

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Impact of cation-based localized electronic states on the conduction and valence band structure of Al1−xInxN alloys

Abstract: Original citationSchulz, S., Caro, M. A. and O'Reilly, E. P. (2014) 'Impact of cationbased localized electronic states on the conduction and valence band structure of Al1−xInxN alloys

Cited by 22 publications

References 38 publications

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Atomistic description of wave function localization effects in In_xGa_1-xN alloys and quantum wells

High internal quantum efficiency ultraviolet to green luminescence peaks from pseudomorphic m-plane Al1−xInxN epilayers grown on a low defect density m-plane freestanding GaN substrate

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Impact of cation-based localized electronic states on the conduction and valence band structure of Al1−xInxN alloys

Abstract: Original citationSchulz, S., Caro, M. A. and O'Reilly, E. P. (2014) 'Impact of cationbased localized electronic states on the conduction and valence band structure of Al1−xInxN alloys

Cited by 22 publications

References 38 publications

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Atomistic description of wave function localization effects in InxGa1-xN alloys and quantum wells

High internal quantum efficiency ultraviolet to green luminescence peaks from pseudomorphic m-plane Al1−xInxN epilayers grown on a low defect density m-plane freestanding GaN substrate

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Atomistic description of wave function localization effects in In_xGa_1-xN alloys and quantum wells