Infrared Optical Properties Of Wurtzite Semiconductor Heterostructure With Arbitrary Crystal Orientations
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Date
2016-03
Authors
Lee, Sai Cheong
Journal Title
Journal ISSN
Volume Title
Publisher
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.
Description
Keywords
Infrared