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Optical Anisotropy Studies of Sapphire by Raman Scattering and Spectroscopic Transmission Ellipsometry

Published online by Cambridge University Press:  10 February 2011

H. Yao ,
C. H. Yan ,
S. P. Denbaars  and
J. M. Zavada
H. Yao
Affiliation:
University of Nebraska, Center for Microelectronic and Optical Material Research, and Department of Electrical Engineering, Lincoln, NE 68588, hyao@unl.edu
C. H. Yan
Affiliation:
University of Nebraska, Center for Microelectronic and Optical Material Research, and Department of Electrical Engineering, Lincoln, NE 68588, hyao@unl.edu
S. P. Denbaars
Affiliation:
University of California, Santa Barbara, CA 93106
J. M. Zavada
Affiliation:
US Army Research Office, Research Triangle Park, NC 27709
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Abstract

Optical anisotropy of sapphire have been studied by both polarized Raman scattering and transmission variable angle spectroscopic ellipsometry (TVASE). The polarized Raman effect was measured on both c-plane (0001) and a-plane (2110) sapphire substrates. Two TO phonons (379 and 431 cm−l) and four LO phonons (418, 450, 577, and 750 cm−1) were observed when the optical axis <c> is perpendicular to the polarization of the incident laser beam (for both c-plane and a-plane). While only two TO phonons (379 and 431cm−1) and two LO phonons (418 and 645 cm−1) can be seen when the optical axis is parallel to the polarization for an a-plane sapphire. The optical axis of the a-plane sapphire can then be quickly determined by either maximizing or minimizing the 645 LO peak intensity with about ±10° error. TVASE measurements were carried out in the energy range of 0.75eV to 5.8eV at room temperature. Sizable off-diagonal Jones matrix elements Apst, and Aspt can be detected even with the optical axis 1° off the X-axis. This indicates that TVASE has a high sensitivity to optical anisotropy. By minimizing these off-diagonal elements and combining the Raman analysis, the optical axis orientation of an a-plane or m-plane (0110) sapphire can therefore be fully determined with an error of less than 1°.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 512: Symposium F – Wide Bandgap Semiconductors for High Power, High Frequency , 1998 , 411
Copyright
Copyright © Materials Research Society 1998

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References

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