Growth and Characterization of CdxZn1-xTe Epilayers and Characterization of InxGa1-xN Epilayers

• Main Authors: Wen-Chung Fan, 范文忠
• Other Authors: Wu-Ching Chou
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/shf38r

碩士 === 中原大學 === 應用物理研究所 === 91 === CdxZn1-xTe epilayers were grown on the GaAs(001) substrates by the molecular beam epitaxy. The optical properties of the epilayers were studied by the reflectance (R) and photoluminescence (PL) measurements. The energy gaps were found to decrease with the Cd concentration. The exciton activation energy, which is determined from the integrated PL intensity versus temperature plot, shows a decrease with the Cd composition. Temperature dependence of the energy gap, measured by the PL spectra, was fitted by the Varshni's and the O'Donnell's relation. Good fits were obtained with both relations for the samples with small Cd concentration. However, for the Cd0.582Zn0.418Te epilayer, the O'Donnell's fit shows more reasonable trend. In addition to the CdxZn1-xTe epilayers, the optical properties of the InxGa1-xN epilayers were investigated by using the PL, R and transmission (T) techniques. The InxGa1-xN epilayers with x = 0, 0.08, 0.10 and 0.15 were grown by metal organic chemical vapor deposition on the sapphire substrate. Sharp PL line-shape was observed. Band-tailing model was employed to explain the reason why the PL peak exhibits energy blue-shift and then red-shift as temperature increases. The effect of Indium mole fraction on the exciton activation energy and the temperature dependent PL line-width were obtained. A preheating of the sapphire substrate at 1300 oC was proved to be essential for the improvement of the epilayer’s optical quality.