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

No Thumbnail Available
s41598-019-43142-5.pdf(2.06 MB)
Published version
41598_2019_43142_MOESM1_ESM.pdf(133.28 KB)
Supplementary file
Bushell, Zoe L.
Broderick, Christopher A.
Nattermann, Lukas
Joseph, Rita
Keddie, Joseph L.
Rorison, Judy M.
Volz, Kerstin
Sweeney, Stephen J.
Journal Title
Journal ISSN
Volume Title
Springer Nature
Research Projects
Organizational Units
Journal Issue
Using spectroscopic ellipsometry measurements on GaP1−xBix/GaP epitaxial layers up to x = 3.7% we observe a giant bowing of the direct band gap ($${E}_{g}^{{\rm{\Gamma }}}$$EgΓ) and valence band spin-orbit splitting energy (ΔSO). $${E}_{g}^{{\rm{\Gamma }}}$$EgΓ(ΔSO) 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 $${E}_{g}^{{\rm{\Gamma }}}$$EgΓand ΔSO 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 $${E}_{g}^{{\rm{\Gamma }}}$$EgΓand ΔSO with x. In contrast to the well-studied GaAs1−xBix alloy, in GaP1−xBix 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 $${E}_{g}^{{\rm{\Gamma }}}$$EgΓand ΔSO 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 GaP1−xBix alloy band structure.
Spectroscopic ellipsometry measurements , Giant bowing , GaP1−xBix
Bushell, Z.L., Broderick, C.A., Nattermann, L., Joseph, R., Keddie, J.L., Rorison, J.M., Volz, K. and Sweeney, S.J. (2019). 'Giant bowing of the band gap and spin-orbit splitting energy in GaP 1− x Bi x dilute bismide alloys'. Scientific reports, 9(1), 6835. (8 pp). doi:10.1038/s41598-019-43142-5