Optical functions and critical points of dilute bismide alloys studied by spectroscopic ellipsometry

Critical point transition energies and optical functions of the novel GaAs-based dilute bismide alloys GaAsBi, GaNAsBi, and GaPAsBi were determined using spectroscopic ellipsometry. The ellipsometry data were analyzed using a parameterized semiconductor model to represent the dielectric function of...

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Bibliographic Details
Published in:Journal of applied physics 2018-01, Vol.123 (4)
Main Authors: Bushell, Z. L., Joseph, R. M., Nattermann, L., Ludewig, P., Volz, K., Keddie, J. L., Sweeney, S. J.
Format: Article
Language:English
Subjects:
Alloy development
Alloys
Applied physics
Band gap
Critical point
Dilution
Gallium arsenide
Oscillators
Photonics
Quaternary alloys
Refractivity
Spectroellipsometry
Splitting
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Summary:Critical point transition energies and optical functions of the novel GaAs-based dilute bismide alloys GaAsBi, GaNAsBi, and GaPAsBi were determined using spectroscopic ellipsometry. The ellipsometry data were analyzed using a parameterized semiconductor model to represent the dielectric function of the alloys as the sum of Gaussian oscillators centered on critical points in the band structure, and from this extracting the energies of those critical points. The band gap and spin-orbit splitting were measured for samples for a range of alloy compositions. The first experimental measurements of the spin-orbit splitting in the GaNAsBi quaternary alloy were obtained, which showed that it is approximately independent of N content, in agreement with theory. The real component of the refractive index in the transparent region below the band gap was found to decrease as the band gap increased for all of the alloys studied, following the usual relations for conventional semiconductors. This work provides key electronic and optical parameters for the development of photonic devices based on these novel alloys.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5006974