Compositional inhomogeneity of a high-efficiency InxGa1−xN based multiple quantum well ultraviolet emitter studied by three dimensional atom probe

Galtrey, M. J.; Oliver, Rachel A.; Kappers, Menno J.; McAleese, C.; Zhu, Dandan; Humphreys, C. J.; Clifton, P. H.; Larson, D.J.; Cerezo, A.

doi:10.1063/1.2829592

Cited by 35 publications

(34 citation statements)

References 9 publications

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“…Such two-temperature growth has been observed to provide high internal quantum efficiencies in both green-and near-ultra-violet-emitting QWs [41,44]. Similar gross well-width fluctuations were also observed in QWs which had been annealed at their growth temperature for durations comparable with those required for the temperature ramp [43].…”

Section: The Impact Of Broader Scale Microstructurementioning

confidence: 65%

“…Instead, they provide a region of increased bandgap around the dislocation, providing a barrier to carrier diffusion to the dislocation, but not necessarily preventing the carriers from moving around freely in other regions of the QW. Since low temperature optical measurements [12], and positron annihilation spectroscopy [11], have suggested very short localisation length scales in InGaN, such "dislocation screening" is unlikely to be the only mechanism influencing carrier diffusion in InGaN QWs, However, reports of very high internal quantum efficiencies in quantum wells in which microstructural characterisation suggests that dislocation screening is occurring [40,41] suggest that it could be an important contributory factor.…”

Section: The Impact Of Broader Scale Microstructurementioning

confidence: 99%

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Microstructural origins of localization in InGaN quantum wells

Oliver¹,

Bennett²,

Zhu³

et al. 2010

J. Phys. D: Appl. Phys.

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The startling success of GaN-based light emitting diodes despite the high density of dislocations found in typical heteroepitaxial material has been attributed to localisation of carriers at non-uniformities in the quantum wells which form the active region of such devices. Here, we review the different possible structures within the quantum wells which could act as localisation sites, at length scales ranging from the atomic to the tens of nanometre range. In some quantum wells several localisation mechanisms could be operational, but the challenge remains to optimise the quantum wells' structure to achieve improved quantum efficiencies, particularly at high excitation powers.

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Section: The Impact Of Broader Scale Microstructurementioning

confidence: 65%

Section: The Impact Of Broader Scale Microstructurementioning

confidence: 99%

Microstructural origins of localization in InGaN quantum wells

Oliver¹,

Bennett²,

Zhu³

et al. 2010

J. Phys. D: Appl. Phys.

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“…However, when the reconstruction of the 3DAP sample for the UVemitting sample is compared with that for the single-temperature samples, there are much more striking differences. Figure 4 shows that there are large 20 -100 nm discontinuities in several of the QW layers [11], in contrast to the broadly flat and uniform layers seen in the singletemperature samples. A more detailed compositional analysis reveals that there are also underlying broad-scale compositional variations.…”

Section: Resultsmentioning

confidence: 79%

Atom probe reveals the structure of In_xGa_1–xN based quantum wells in three dimensions

Galtrey

Oliver

Kappers

et al. 2008

Physica Status Solidi (b)

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The three‐dimensional atom probe has been used to characterize Inx Ga1–x N based multiple quantum well structures emitting from the green to the ultra‐violet with sub‐nanometre resolution over a 100 nm field of view. The results show gross discontinuities and compositional variations within the UV‐emitting quantum well layers on a 20–100 nm length scale. We propose that these may contribute to the high efficiency of this structure. In addition, the analysis shows the presence of indium in the barrier layers of all the samples, whether or not there was an indium precursor present during barrier growth. The distribution of indium within the blue‐ and green‐emitting Inx Ga1–x N quantum wells is also analyzed, and we find no evidence that Inx Ga1–x N with a range of compositions is not a random alloy, and so rule out indium clustering as the cause of the reported carrier localization in these structures. The upper interface of each quantum well layer is shown to be rougher and more diffuse than the lower, and the existence of monolayer steps in the interfaces that could effectively localize carriers at room temperature is revealed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…We have recently discovered that gross well-width fluctuations are present in a 2T near-UV-emitting MQW sample grown at Cambridge with a world-leading internal quantum efficiency [23]. This further illustrates the importance of understanding and optimising network structures and there role in luminescence.…”

Section: Invited Articlementioning

confidence: 97%

Gross well‐width fluctuations in InGaN quantum wells

Oliver

Kappers

Humphreys

2008

Phys. Status Solidi (c)

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In our earlier studies, we showed that the InxGa1–xN quantum wells in some green‐emitting commercial light emitting diodes are highly non‐uniform, containing gross width fluctuations on a 50–100 nm lateral scale. We reproduced such fluctuations in a research laboratory context by either annealing the InxGa1–xN epilayer, or subjecting it to a temperature ramp prior to growth of the GaN cap. We showed that the width fluctuations relate to a network of interlinking InxGa1–xN strips, and that threading dislocations tend to intersect this network between the strips. Here we investigate whether such networks may also be formed under a range of other growth conditions. By examining very thin InxGa1–xN epilayers which are expected to be fully strained, and showing they form networks upon thermal treatment, we rule out any role of strain relaxation in network formation. By examining samples grown at temperatures up to 790 °C, with low indium contents, and observing the formation of a network structure, we eliminate the possibility that spinodal decomposition is involved in network formation. The growth conditions examined are relevant to blue and ultra‐violet light emitters, and we thus suggest that network structures may have broader implications than previously realised. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Compositional inhomogeneity of a high-efficiency InxGa1−xN based multiple quantum well ultraviolet emitter studied by three dimensional atom probe

Cited by 35 publications

References 9 publications

Microstructural origins of localization in InGaN quantum wells

Microstructural origins of localization in InGaN quantum wells

Atom probe reveals the structure of In_xGa_1–xN based quantum wells in three dimensions

Gross well‐width fluctuations in InGaN quantum wells

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Compositional inhomogeneity of a high-efficiency InxGa1−xN based multiple quantum well ultraviolet emitter studied by three dimensional atom probe

Cited by 35 publications

References 9 publications

Microstructural origins of localization in InGaN quantum wells

Microstructural origins of localization in InGaN quantum wells

Atom probe reveals the structure of InxGa1–xN based quantum wells in three dimensions

Gross well‐width fluctuations in InGaN quantum wells

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Product

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Atom probe reveals the structure of In_xGa_1–xN based quantum wells in three dimensions