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Far Infrared Spectroscopy Studies of Composition Dependent Cd1-xZnxTe, CdSexTe1-x and AlxGa1-xAs/GaAs

By 施彥豪 and Yen Hao Shih

Abstract

[[abstract]]Fourier transform infrared spectroscopy (FTIR) Bruker IFS 66 V/S and low temperature system were employed for a series of measurements. The samples were measured at room temperature (300 K) and some of them were measured at low temperature (80 K). A dielectric response model was used to determine the optical and transport properties of the samples. Different compositions of Cd1-xZnxTe bulks, CdSexTe1-x bulks and AlxGa1-xAs thin film grown on GaAs were used in this study. From far infrared spectrum of Cd1-xZnxTe, we found a small peak appears on the top of the phonon mode when x?0 and x?1 (In other words, the pure CdTe and ZnTe materials). This small peak disappears quickly with the variation of Zn composition. The small peak was caused by the clustering between anions and cations from previous studies. The CdTe-like and ZnTe-like TO frequencies increase with the increase of Zn composition x. From far infrared spectrum of CdSexTe1-x, when x?0, there is a clustering effect similar as Cd1-xZnxTe and the peak becomes stronger with decreasing temperature. However, the peak disappears soon with increasing Se composition. Besides, a third mode appeared between the CdTe-like phonon mode and CdSe-like phonon mode and becomes stronger with an increase of Se composition. We thought the third mode behavior was caused by the wurtzite structure of CdSe. This opinion has a good agreement with previous studies. From far infrared spectrum of AlxGa1-xAs/GaAs, the AlAs-like phonon frequency increases with increasing x and GaAs-like phonon mode decreases with increasing x. Besides, we found a variation of the GaAs-like mode strength cause by the second reflection. This study characterized the high-frequency dielectric constant, transverse optical phonon mode frequency, strength, damping constant, free carrier concentration, mobility and effective mass of Cd1-xZnxTe, CdSexTe1-x and AlxGa1-xAs/GaAs. Conductivity and force constant between the atoms were also calculated. The variations of these parameters with composition have been characterized. Besides, the special structure change of CdSexTe1-x is observed clearly in the spectrum and has discussed. The study established a data base of these materials and provides a fundamental property for their application reference.

Topics: 遠紅外線光譜;砷化鋁鎵;碲化鎘鋅;碲化鎘硒;光學聲子;傳導性質, Far Infrared Spectroscopy;AlGaAs;CdZnTe;CdSeTe;Optic phonon;Electrical Properties, [[classification]]38
Year: 2011
OAI identifier: oai:ir.lib.ntnu.edu.tw:309250000Q/70612
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