Band gap bowing and optical polarization switching in Al1−xGaxN alloys

We present a detailed theoretical study of the band gap bowing of wurtzite AlGaN alloys over the full composition range. Our theoretical framework is based on an atomistic tight‐binding model, including local strain and built‐in potential variations due to random alloy fluctuations. We extract a bow...

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Bibliographic Details
Published in:physica status solidi (b) 2015-05, Vol.252 (5), p.879-884
Main Authors: Coughlan, Conor, Schulz, Stefan, Caro, Miguel A., O'Reilly, Eoin P.
Format: Article
Language:English
Subjects:
AlGaN
band gap
crystal field splitting
optical polarization
tight binding
Online Access:Get full text
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Summary:We present a detailed theoretical study of the band gap bowing of wurtzite AlGaN alloys over the full composition range. Our theoretical framework is based on an atomistic tight‐binding model, including local strain and built‐in potential variations due to random alloy fluctuations. We extract a bowing parameter for the band gap of b=0.94 eV, which is in good agreement with experimental data. Our analysis shows that the bowing of the band gap mainly arises from bowing of the conduction band edge; for the composition dependence of the valence band edge energy we find a close to linear behavior. Finally, we investigate the wave function character of the valence band edge as a function of GaN content x. Our analysis reveals an optical polarization switching around x=0.75, which is in the range of reported experimental data.
ISSN:0370-1972
1521-3951
DOI:10.1002/pssb.201451593