Infrared Optical Properties Of Wurtzite Semiconductor Heterostructure With Arbitrary Crystal Orientations

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Date
2016-03
Authors
Lee, Sai Cheong
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Universiti Sains Malaysia
Abstract
Crystal orientation dependence of the infrared (IR) optical properties of hexagonal wurtzite III-nitride heterostructures and their relevant substrates was investigated. Polarized IR reflectance measurements showed that the spectral responses of bulk sapphire crystals and wurtzite III-nitride heterostructures consisting of layers with arbitrary crystallographic planes depend on sample orientation. Except for sample with c-plane oriented surface, the polarized IR reflectance spectra of a given sample can be changed by rotating the sample about its surface normal. A reflection formula that considers the effect of crystal orientation was employed with a curve fitting procedure to analyze the measured spectra. Important materials parameters such as the dielectric constant, optical phonon modes, layer thickness and crystal orientation of the studied samples, have been non-destructively determined from the best-fit of experimental and theoretical polarized IR reflectance spectra. Using the obtained parameters, simulations of the surface and interface phonon polaritons (SPhP and IPhP) dispersion spectra have been performed by taking into account the effects of damping parameters and crystal orientation. The theoretical results revealed that the SPhP and IPhP responses of samples with non-polar a-plane or semi-polar r-plane oriented surfaces are directionallydependent. The predicted resonant properties of the SPhP and IPhP modes were in good agreement with the p-polarized IR attenuated total reflectance measurements.
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Infrared
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