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Ge1-xSnx alloys: Consequences of band mixing effects for the evolution of the band gap Γ-character with Sn concentration

Eales, Timothy D., Marko, Igor P., Schulz, Stefan, O’Halloran, Edmond, Ghetmiri, Seyed, Du, Wei, Zhou, Yiyin, Yu, Shui-Qing, Margetis, Joe, Tolle, John , O’Reilly, Eoin P. and Sweeney, Stephen J. (2019) Ge1-xSnx alloys: Consequences of band mixing effects for the evolution of the band gap Γ-character with Sn concentration Scientific Reports.

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Sci Rep 2019 - Evolution of Γ-Character with Alloy Concentration in Ge1-xSnx Alloys - accepted version.pdf - Accepted version Manuscript
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In this work we study the nature of the band gap in GeSn alloys for use in silicon-based lasers. Special attention is paid to Sn-induced band mixing effects. We demonstrate from both experiment and ab-initio theory that the (direct) Γ- character of the GeSn band gap changes continuously with alloy composition and has significant Γ-character even at low (6%) Sn concentrations. The evolution of the Γ-character is due to Sn-induced conduction band mixing effects, in contrast to the sharp indirect-to-direct band gap transition obtained in conventional alloys such as Al1-xGaxAs. Understanding the band mixing effects is critical not only from a fundamental and basic properties viewpoint but also for designing photonic devices with enhanced capabilities utilizing GeSn and related material systems.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Eales, Timothy
Marko, Igor
Schulz, Stefan
O’Halloran, Edmond
Ghetmiri, Seyed
Du, Wei
Zhou, Yiyin
Yu, Shui-Qing
Margetis, Joe
Tolle, John
O’Reilly, Eoin P.
Sweeney, Stephen
Date : 29 August 2019
Funders : EPSRC - Engineering and Physical Sciences Research Council, Science Foundation Ireland
Copyright Disclaimer : Copyright 2019 The Authors
Uncontrolled Keywords : Germanium tin; Group IV; Si photonics; Direct band gap
Additional Information : This work was supported in part by the EPSRC (UK) Projects EP/H005587/01, and EP/N021037/1, and in part by Science Foundation Ireland (13/SIRG/2210, 14/IA/2513, 15/IA/3082), with computing resources at Tyndall National Institute supported by Science Foundation Ireland (SFI) and at Irish Centre for High End Computing (ICHEC) funded by SFI and Higher Education Authority. T. D. Eales was supported by EPSRC (UK) through a Ph.D. studentship. W. Yu appreciates support from National Science Foundation (NSF) under DMR-1149605 and from the Air Force Office of Scientific Research (AFOSR) under FA9550-14-1-0205. The authors would also like to thank B. N. Murdin for advice on the preparation and contents of the manuscript. The data associated with this work are available from the University of Surrey publications repository at
Depositing User : Diane Maxfield
Date Deposited : 16 Sep 2019 11:35
Last Modified : 25 Nov 2019 15:27

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