The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem

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dc.contributor.authorHumphreys, C. J.
dc.contributor.authorGriffiths, J. T.
dc.contributor.authorTang, F.
dc.contributor.authorOehler, F.
dc.contributor.authorFindlay, S. D.
dc.contributor.authorZheng, C.
dc.contributor.authorEtheridge, J.
dc.contributor.authorMartin, T. L.
dc.contributor.authorBagot, P. A. J.
dc.contributor.authorMoody, M. P.
dc.contributor.authorSutherland, D.
dc.contributor.authorDawson, Philip
dc.contributor.authorSchulz, Stefan
dc.contributor.authorZhang, S.
dc.contributor.authorFu, W. Y.
dc.contributor.authorZhu, T.
dc.contributor.authorKappers, M. J.
dc.contributor.authorOliver, R. A.
dc.contributor.funderEngineering and Physical Sciences Research Council
dc.date.accessioned2017-09-26T11:39:18Z
dc.date.available2017-09-26T11:39:18Z
dc.date.issued2017
dc.description.abstractWe have used high resolution transmission electron microscopy (HRTEM), aberration-corrected quantitative scanning transmission electron microscopy (Q-STEM), atom probe tomography (APT) and X-ray diffraction (XRD) to study the atomic structure of (0001) polar and (11-20) non-polar InGaN quantum wells (QWs). This paper provides an overview of the results. Polar (0001) InGaN in QWs is a random alloy, with In replacing Ga randomly. The InGaN QWs have atomic height interface steps, resulting in QW width fluctuations. The electrons are localised at the top QW interface by the built-in electric field and the well-width fluctuations, with a localisation energy of typically 20meV. The holes are localised near the bottom QW interface, by indium fluctuations in the random alloy, with a localisation energy of typically 60meV. On the other hand, the non-polar (11-20) InGaN QWs contain nanometre-scale indium rich clusters which we suggest localise the carriers and produce longer wavelength (lower energy) emission than from random alloy non-polar InGaN QWs of the same average composition. The reason for the indium-rich clusters in non-polar (11-20) InGaN QWs is not yet clear, but may be connected to the lower QW growth temperature for the (11-20) InGaN QWs compared to the (0001) polar InGaN QWs. (C) 2017 The Authors. Published by Elsevier B.V.en
dc.description.sponsorshipEngineering and Physical Sciences Research Council (EP/J001627/1, EP/I01259/1, EP/J003603/1)en
dc.description.statusPeer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationHumphreys, C. J., Griffiths, J. T., Tang, F., Oehler, F., Findlay, S. D., Zheng, C., Etheridge, J., Martin, T. L., Bagot, P. A. J., Moody, M. P., Sutherland, D., Dawson, P., Schulz, S., Zhang, S., Fu, W. Y., Zhu, T., Kappers, M. J. and Oliver, R. A. (2017) 'The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem', Ultramicroscopy, 176 (6pp). doi: 10.1016/j.ultramic.2017.01.019en
dc.identifier.doi10.1016/j.ultramic.2017.01.019
dc.identifier.endpage98
dc.identifier.issn0304-3991
dc.identifier.journaltitleUltramicroscopyen
dc.identifier.startpage93
dc.identifier.urihttps://hdl.handle.net/10468/4782
dc.identifier.volume176
dc.language.isoenen
dc.publisherElsevier Science BVen
dc.relation.urihttp://www.sciencedirect.com/science/article/pii/S0304399117300487?via%3Dihub
dc.rights© 2017, the Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectGallium nitrideen
dc.subjectAtomic structureen
dc.subjectQuantum wellsen
dc.subjectQuantitative STEMen
dc.subjectAberration-corrected electron microscopyen
dc.subjectTransmission electron microscopyen
dc.subjectHeterostructuresen
dc.subjectEmissionen
dc.subjectStrainen
dc.subjectAlloysen
dc.subjectGrowthen
dc.subjectShiften
dc.subjectDotsen
dc.titleThe atomic structure of polar and non-polar InGaN quantum wells and the green gap problemen
dc.typeArticle (peer-reviewed)en
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