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Band gap bowing and optical polarization switching in Al 1 − x Ga x N alloys
Author(s) -
Coughlan Conor,
Schulz Stefan,
Caro Miguel A.,
O'Reilly Eoin P.
Publication year - 2015
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201451593
Subject(s) - bowing , band gap , wurtzite crystal structure , materials science , condensed matter physics , wide bandgap semiconductor , semimetal , polarization (electrochemistry) , electronic band structure , direct and indirect band gaps , valence band , optoelectronics , physics , chemistry , philosophy , theology , zinc , metallurgy
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.