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Optical Characteristics of Amorphous III-V Nitride Thin Films

Published online by Cambridge University Press:  01 February 2011

Jebreel M. Khoshman
Affiliation:
Department of Physics & Astronomy, Condensed Matter & Surface Science Program, Ohio University, Athens, OH 45701
Martin E. Kordesch
Affiliation:
Department of Physics & Astronomy, Condensed Matter & Surface Science Program, Ohio University, Athens, OH 45701
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Abstract

The optical constants and polarized optical properties of amorphous III-V nitride thin films, a-(Al, Ga, In) N, deposited by RF magnetron sputtering onto crystalline silicon, c-Si, (111) and glass substrates have been investigated over the wavelength range 300 – 1400 nm. The optical constants of a-AlN were obtained by analysis of the measured ellipsometric spectra through the Cauchy–Urbach model while the optical constants of a-(In, Ga) N were determined using the Tauc-Lorentz model. Analysis of the absorption coefficient of a-AlN (in the range 200 – 1400 nm) and a-GaN (in the range 300 – 1400 nm) show the optical bandgap to be 5.9 ± 0.05 and 3.44 ± 0.05 eV. The absorption coefficient of a-InN (in the range 300 – 1400 nm) as a function of photon energy shows the absorption edge to be about 1.74 ± 0.05 eV. From the angle dependence of the p-polarized reflectivity we deduced Brewster and principal angles of these films. Measurement of the polarized optical properties revealed a high transmissivity (70 % – 95 %) and low absorptivity (< 18 %) for all three thin films in the visible and near infrared regions.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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