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

Conor Coughlan; Stefan Schulz; Miguel A. Caro; Eoin P. O'Reilly

doi:10.1002/pssb.201451593

Band gap bowing and optical polarization switching in Al_1-xGa_xN alloys

Conor Coughlan, Stefan Schulz^*, Miguel A. Caro, Eoin P. O'Reilly

^*Corresponding author for this work

Department of Electrical Engineering and Automation

University College Cork

Research output: Contribution to journal › Article › Scientific › peer-review

Abstract

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.

Original language	English
Pages (from-to)	879-884
Number of pages	6
Journal	PHYSICA STATUS SOLIDI B: BASIC SOLID STATE PHYSICS
Volume	252
Issue number	5
DOIs	https://doi.org/10.1002/pssb.201451593
Publication status	Published - 1 May 2015
MoE publication type	A1 Journal article-refereed

Keywords

AlGaN
Band gap
Crystal field splitting
Optical polarization
Tight binding

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10.1002/pssb.201451593

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title = "Band gap bowing and optical polarization switching in Al1-xGaxN alloys",

abstract = "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.",

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AU - Coughlan, Conor

AU - Schulz, Stefan

AU - Caro, Miguel A.

AU - O'Reilly, Eoin P.

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N2 - 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.

AB - 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.

KW - AlGaN

KW - Band gap

KW - Crystal field splitting

KW - Optical polarization

KW - Tight binding

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Band gap bowing and optical polarization switching in Al_1-xGa_xN alloys

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Keywords

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