Optical anisotropy of GaN/sapphire studied by generalized ellipsometry and Raman scattering

Chunhui Yan; H. Walter Yao; James M. Van Hove; Andrew M. Wowchak; Peter P. Chow; John M. Zavada

doi:10.1117/12.344490

14 April 1999 Optical anisotropy of GaN/sapphire studied by generalized ellipsometry and Raman scattering

Chunhui Yan, H. Walter Yao, James M. Van Hove, Andrew M. Wowchak, Peter P. Chow, John M. Zavada

Proceedings Volume 3621, Light-Emitting Diodes: Research, Manufacturing, and Applications III; (1999) https://doi.org/10.1117/12.344490
Event: Optoelectronics '99 - Integrated Optoelectronic Devices, 1999, San Jose, CA, United States

Abstract

Generalized variable angle spectroscopic ellipsometry (VASE) and Raman scattering have been employed to study the optical anisotropy of GaN/Sapphire structures. The GaN films were grown hydride vapor phase epitaxy and molecular beam epitaxy on both m-plane and c-plane sapphire ((alpha) -Al₂O₃) substrates, respectively. Anisotropic optical phonon structure of sapphire have been measured, based on which the optical axis of sapphire substrate has been determined. A 541 cm^-1 TO phonon of GaN grown on m-plane sapphire substrate has been discovered experimentally which is due the coupling of A₁ and E₁ TOs. Optical axis orientation of GaN film on m-sapphire has been fully determined by the anisotropic angular dependence of the coupled TO phonon. Off-diagonal elements A_pst and A_spt of transmission VASE (TVASE) are very sensitive parameters related to the optical anisotropy. The optical axis orientation of GaN on m-sapphire has also been accurately determined by TVASE at two special sample positions. The optical anisotropy due to GaN film and sapphire substrate has been successfully separated at 90 degree(s) samples position allowing to study the optical anisotropy of GaN film only.

Citation Download Citation

Chunhui Yan, H. Walter Yao, James M. Van Hove, Andrew M. Wowchak, Peter P. Chow, and John M. Zavada "Optical anisotropy of GaN/sapphire studied by generalized ellipsometry and Raman scattering", Proc. SPIE 3621, Light-Emitting Diodes: Research, Manufacturing, and Applications III, (14 April 1999); https://doi.org/10.1117/12.344490

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KEYWORDS

Gallium nitride

Sapphire

Phonons

Anisotropy

Raman scattering

Raman spectroscopy

Astatine

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