Longitudinal optical phonon-plasmon-coupled modes in epitaxial GaN films on sapphire substrate

Z.F. Li; Wei Lu; H.-J. Ye; Xianzhang Yuan; Shuechu Shen; G. Li; Soo-Jin Chua

doi:10.1117/12.408456

29 November 2000 Longitudinal optical phonon-plasmon-coupled modes in epitaxial GaN films on sapphire substrate

Z.F. Li, Wei Lu, H.-J. Ye, Xianzhang Yuan, Shuechu Shen, G. Li, Soo-Jin Chua

Proceedings Volume 4086, Fourth International Conference on Thin Film Physics and Applications; (2000) https://doi.org/10.1117/12.408456
Event: 4th International Conference on Thin Film Physics and Applications, 2000, Shanghai, China

Abstract

We have studied the longitudinal optical phonon-plasmon coupled (LPP) modes in device quality GaN epitaxy thin films deposited on sapphire substrate using infrared reflection spectroscopy. By theoretical calculation and fitting with the experimental IR reflection spectra for a series of Si doped GaN epilayers we obtain the phonon vibration parameters and the plasmon frequency and damping constant in GaN. The LPP modes have been deduced by the imaginary parts of the reciprocal dielectric function in IR reflection measurement. Both high and low branches of the LO phonon- plasmon coupling mode (LPP⁺ and LPP^-) are well resolved. With the increase of doping level, the frequency of the LPP⁺ mode shifts to higher while that of the LPP^- mode trends toward TO phonon of GaN. The carrier concentration and mobility in GaN have also been deduced. The IR measured concentration of carriers coincides with the Hall measurement. The mobility ratio of Hall to IR is about 1.75 approximately 1.96, implying a dominating mechanism of ionized impurity scattering. Raman measurement has also been performed on the same series of samples. The spectral reveal the similar behavior of the LPP modes to that in IR measurement. Our results show that both IR reflection and Raman scattering are powerful and nondestructive tools to investigate the carrier properties in GaN thin films.

Citation Download Citation

Z.F. Li, Wei Lu, H.-J. Ye, Xianzhang Yuan, Shuechu Shen, G. Li, and Soo-Jin Chua "Longitudinal optical phonon-plasmon-coupled modes in epitaxial GaN films on sapphire substrate", Proc. SPIE 4086, Fourth International Conference on Thin Film Physics and Applications, (29 November 2000); https://doi.org/10.1117/12.408456

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KEYWORDS

Gallium nitride

Raman spectroscopy

Raman scattering

Sapphire

Thin films

Phonons

Plasmons

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