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Optical Band Gap Measurements of InN Films in the Strong Degeneracy Limit

Published online by Cambridge University Press:  11 February 2011

D. B. Haddad
Affiliation:
Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201
J. S. Thakur
Affiliation:
Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202
V. M. Naik
Affiliation:
Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
G. W. Auner
Affiliation:
Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202
R. Naik
Affiliation:
Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201
L. E. Wenger
Affiliation:
Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201
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Abstract

The optical properties of InN thin films (0.5 μm thick) grown on sapphire substrates by plasma source molecular beam epitaxy deposition have been measured in order to study the effect of electron degeneracy on the band gap measurement. X-ray diffraction measurements show that the films are wurtzite polycrystalline at a growth temperature of 325 °C, whereas a completely c-axis textured growth at a temperature of 475°C. The Raman bands A1 (LO) and E2 are rather broad indicating the presence of a large number of structural defects. Hall effect measurements show that both the films are n-type with carrier concentrations of (8.0 ± 1.6) × 1020 cm−3 and (3 ± 0.6) × 1020cm−3, respectively. The optical absorption data on these samples show n dependent band gap edge and a peak corresponding to plasmon due to strong electron degeneracy. The band gap absorption data were analyzed assuming a direct band gap and incorporating the Moss-Burstein shift effect. By taking into account the non-parabolic dispersion and the band-renormalization effects for the conduction band of InN, the calculated true band gap (0.7 eV) agrees with other recent measurements on high quality InN films.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

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