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Giant bowing of the band gap and spin-orbit splitting energy in GaP1−χBiχ dilute bismide alloys

Bushell, Zoe L., Broderick, Christopher A., Nattermann, Lukas, Joseph, Rita, Keddie, Joseph L., Rorison, Judy M., Volz, Kerstin and Sweeney, Stephen J. (2019) Giant bowing of the band gap and spin-orbit splitting energy in GaP1−χBiχ dilute bismide alloys Scientific Reports, 9 (1), 6835.

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Using spectroscopic ellipsometry measurements on GaP1−χBiχ/GaP epitaxial layers up to χ = 3.7% we observe a giant bowing of the direct band gap (EΓg) and valence band spin-orbit splitting energy (ΔSO). EΓgSO) is measured to decrease (increase) by approximately 200 meV (240 meV) with the incorporation of 1% Bi, corresponding to a greater than fourfold increase in ΔSO in going from GaP to GaP0.99Bi0.01. The evolution of EΓg and ΔSO with χ is characterised by strong, composition-dependent bowing. We demonstrate that a simple valence band-anticrossing model, parametrised directly from atomistic supercell calculations, quantitatively describes the measured evolution of EΓg and ΔSO with χ. In contrast to the well-studied GaAs1−χBiχ alloy, in GaP1−χBiχ substitutional Bi creates localised impurity states lying energetically within the GaP host matrix band gap. This leads to the emergence of an optically active band of Bi-hybridised states, accounting for the overall large bowing of EΓg and ΔSO and in particular for the giant bowing observed for χ ≲ 1%. Our analysis provides insight into the action of Bi as an isovalent impurity, and constitutes the first detailed experimental and theoretical analysis of the GaP1−χBiχ alloy band structure.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Bushell, Zoe
Broderick, Christopher A.
Nattermann, Lukas
Joseph, Rita
Keddie, Joseph
Rorison, Judy M.
Volz, Kerstin
Sweeney, Stephen
Date : 2 May 2019
DOI : 10.1038/s41598-019-43142-5
Copyright Disclaimer : Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit
Depositing User : Clive Harris
Date Deposited : 17 Jul 2019 14:12
Last Modified : 17 Jul 2019 14:12

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