First-principles theory of direct-gap optical emission in hexagonal Ge and its enhancement via strain engineering

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dc.contributor.authorBroderick, Christopher A.
dc.contributor.authorZhang, Xie
dc.contributor.authorTuriansky, Mark E.
dc.contributor.authorVan de Walle, Chris G.
dc.contributor.funderHorizon 2020 Framework Programme
dc.contributor.funderOffice of Science, SC
dc.contributor.funderH2020 Marie Skłodowska-Curie Actions, MSCA, 101030927
dc.contributor.funderNational Energy Research Scientific Computing Center, NERSC, m934-2024
dc.contributor.funderU.S. Department of Energy, ERDA, DE-SC0010689-DE-AC02-05CH11231
dc.contributor.funderResearch Ireland, URF/R1/231340
dc.contributor.funderNational Natural Science Foundation of China, NNSF, 92577119
dc.date.accessioned2026-05-28T13:50:03Z
dc.date.available2026-05-28T13:50:03Z
dc.date.issued2026-04-21
dc.description.abstractThe emergence of hexagonal Ge (2H-Ge) as a candidate direct-gap group-IV semiconductor for Si photonics mandates a rigorous understanding of its optoelectronic properties. Theoretical predictions of a “pseudodirect” band gap, characterized by weak oscillator strength, contrast with a claimed high radiative recombination coefficient B comparable to conventional (cubic) InAs. We compute B in 2H-Ge from first principles and quantify its dependence on temperature, carrier density, and strain. For unstrained 2H-Ge, our calculated spontaneous emission spectra corroborate that measured photoluminescence corresponds to direct-gap emission, but with B being approximately three orders of magnitude lower than in InAs. We confirm a pseudodirect-to-direct-gap transition under ∼2% [0001] uniaxial tension, which can enhance B by up to 3 orders of magnitude, making it comparable to that of InAs. Beyond quantifying the strong enhancement of B via strain engineering, our analysis suggests the dominance of additional, as-yet unquantified recombination mechanisms in this nascent material.en
dc.description.sponsorshipC.A.B. was supported by the European Commission's Horizon 2020 research and innovation program via a Marie Skłodowska-Curie Actions Individual Fellowship (H2020-MSCA-IF
dc.description.sponsorshipGlobal Fellowship “SATORI”, Grant Agreement No. 101030927), and by a Royal Society-Research Ireland University Research Fellowship (RS-RI URF
dc.description.sponsorshipGrant No. URF/R1/231340). M.E.T. and C.G.VdW. were supported by the U.S. Department of Energy (DOE
dc.description.sponsorshipGrant No. DE-SC0010689). X.Z. was supported by the National Natural Science Foundation of China (NSFC
dc.description.sponsorshipGrant No. 92577119). This work used resources of the National Energy Research Scientific Computing Center (Project No. m934-2024), a DOE Office of Science User Facility supported by the Office of Science of the U.S. DOE (Contract No. DE-AC02-05CH11231). C.A.B. thanks Prof. Jos E. M. Haverkort (TU Eindhoven, Netherlands) for useful discussions.
dc.description.versionPublished Version
dc.format.extent8
dc.format.mimetypeapplication/pdfen
dc.identifier.articleid044603
dc.identifier.authororcidBroderick, Christopher A.§0000-0002-5370-7582
dc.identifier.authororcidZhang, Xie
dc.identifier.authororcidTuriansky, Mark E.
dc.identifier.authororcidVan de Walle, Chris G.
dc.identifier.citationBroderick, C A, Zhang, X, Turiansky, M E & Van de Walle, C G 2026, 'First-principles theory of direct-gap optical emission in hexagonal Ge and its enhancement via strain engineering', Physical Review Materials, vol. 10, no. 4, 044603, pp. 1-8. https://doi.org/10.1103/4m4m-84p3
dc.identifier.doi10.1103/4m4m-84p3
dc.identifier.endpage8
dc.identifier.issn2475-9953
dc.identifier.issued4
dc.identifier.journaltitlePhysical Review Materials
dc.identifier.otherRIS: urn:D7993B3B2C1A8945046AE41E13FE2A34
dc.identifier.otherORCID: /0000-0002-5370-7582/work/216088867
dc.identifier.startpage1
dc.identifier.urihttps://hdl.handle.net/10468/18931
dc.identifier.volume10
dc.language.isoen
dc.publisherAmerican Physical Society
dc.relation.urihttps://www.scopus.com/pages/publications/105036476258
dc.relation.urihttps://www.scopus.com/pages/publications/105036476258?origin=resultslist
dc.rights© 2026, the Authors. Published by the American Physical Society.
dc.rights.accessrightsopen access
dc.rights.licensenameAttribution 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.statusPeer reviewed
dc.subjectArsenic compounds
dc.subjectEmission spectroscopy
dc.subjectEnergy gap
dc.subjectFirst-principle theory
dc.subjectGallium phosphide
dc.subjectGermanium compounds
dc.subjectGroup-IV semiconductors
dc.subjectIII-V semiconductors
dc.subjectInAs
dc.subjectNarrow band gap semiconductors
dc.subjectOptical emissions
dc.subjectOptoelectronics property
dc.subjectOscillator strengths
dc.subjectRadiative recombination
dc.subjectRecombination coefficient
dc.subjectSi photonics
dc.subjectSpontaneous emission
dc.subjectStrain engineering
dc.subject[Physics]
dc.titleFirst-principles theory of direct-gap optical emission in hexagonal Ge and its enhancement via strain engineeringen
dc.typeArticle (peer-reviewed)
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