Surface And Interface Phonon Polaritons Characteristics In InAIGaN Quaternary Alloys

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Date
2016-03
Authors
Aljameel, Abdulaziz Ibraheem A
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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.
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Quaternary
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