Surface And Interface Phonon Polaritons Characteristics In InAIGaN Quaternary Alloys
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Date
2016-03
Authors
Aljameel, Abdulaziz Ibraheem A
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
In this project the optical properties of two sets of quaternary nitride films
have been investigated experimentally and theoretically. The first set is the
quaternary nitride InxAlyGa1-x-yN with constant aluminum (Al), y=0.06 and varied
indium (In) mole fraction ranging from 0 ≤ x ≤ 0.10, while the second set is with
constant In, x = 0.10, and variable Al composition ranging from 0 ≤ y ≤ 0.20. In this
study various non-contact and non-destructive characterization tools were used.
These include polarized infrared (IR) reflectance and polarized IR attenuated total
reflection (ATR) spectroscopy for optical characterization. In the first category of
this work the features of the polarized IR reflectance spectra and the optical
characteristics of InxAlyGa1-x-yN were investigated. Based on the anisotropic
dielectric function model, the experimental IR reflectance spectra were numerically
fitted by the theoretical IR reflectance spectra. Good agreement between the
measured and calculated spectra has been obtained. From the fit of the experimental
curves, the reststrahlen parameters at the center of Brillouin zone were determined.
In the second category, the surface phonon polariton (SPP) properties and the effect
of the alloys composition, x, and y on the SPP for ternary and quaternary alloys were
investigated. The scope of study covers both theoretical approach and experimental
works in order to contribute to the understanding of the fundamental properties of the
materials. The surface polariton (SP) dispersion relations were studied theoretically
based on an anisotropy model. These results indicate that the SPP modes of AlxGa1-
xN, InxGa1-xN and AlxIn1-xN are strongly dependent on the Al and In compositions, x, and the behaviour of the SPP modes of AlxGa1-xN and InxGa1-xN can be classified as
one-mode (OM) behaviour, while for the AlxIn1-xN the SPP mode can be classified as
mixed-modes (MM) behaviour. The behaviour of the SPP mode in the InxAl0.06Ga1-x-
0.06N quaternary alloys can be classified as two-mode behaviour and existed in two
branches, A and B. It is clearly seen that the frequency of the interface phonon
polariton (IPP) mode gradually decreases as the x increases for all branches (SPP and
IPP). The data also shows the Al composition dependence of the SPP modes for the
In0.10AlyGa1-0.10-yN quaternary alloys in two branches (at y=0.05 only), branch A and
B. It is clearly seen that the frequency of the SPP mode in branch A gradually
decreases as the y increases and the SPP mode exhibits MM behaviour. Also it is
clearly seen that the frequency of the IPP mode gradually decreases as y increases up
to y=0.10 and then the IPP mode gradually increases as the y further increases.
However, the material properties of the alloy materials formed are dependent on the
alloy composition and typically can be represented by a linear or non-linear
interpolation between its constituents.
Description
Keywords
Quaternary