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Publication - Professor Judy Rorison

    Giant bowing of the band gap and spin-orbit splitting energy in GaP 1−x Bi x dilute bismide alloys

    Citation

    Bushell, ZL, Broderick, CA, Nattermann, L, Joseph, R, Keddie, JL, Rorison, JM, Volz, K & Sweeney, SJ, 2019, ‘Giant bowing of the band gap and spin-orbit splitting energy in GaP 1−x Bi x dilute bismide alloys’. Scientific Reports, vol 9.

    Abstract


    Using spectroscopic ellipsometry measurements on GaP
    1−x
    Bi
    x
    /GaP epitaxial layers up to x = 3.7% we observe a giant bowing of the direct band gap (EgΓ) and valence band spin-orbit splitting energy (Δ
    SO
    ). EgΓ (Δ
    SO
    ) 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 Δ
    SO
    in going from GaP to GaP
    0.99
    Bi
    0.01
    . The evolution of EgΓ and Δ
    SO
    with x 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 EgΓ and Δ
    SO
    with x. In contrast to the well-studied GaAs
    1−x
    Bi
    x
    alloy
    ,
    in GaP
    1−x
    Bi
    x
    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 EgΓ and Δ
    SO
    and in particular for the giant bowing observed for x ≲ 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 GaP
    1−x
    Bi
    x
    alloy band structure.

    Full details in the University publications repository