Transmission Electron Microscopy Studies of InGaN/GaN Multiple Quantum Wells with Different Interfacial Layers and Zinc Oxide Nano-structures
| Autor: | Cheng-Ming Wu, 吳政珉 |
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| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 In this research, we compare four InGaN/GaN multiple quantum-well (QW) samples (un-doped wells and silicon-doped barriers) of different interfacial layers in nanostructures and optical property. In two of the samples, InN interfacial layers are placed between wells and barriers for improving the QW interface quality and hence the photon emission efficiency, particularly with InN layers of no silicon doping. Then, the broadening of InGaN well layer in other sample by inserting silicon-doped InGaN interfacial layers leads to quantum dot-like structures and the strongest carrier localization. Therefore, we observe quite high photoluminescence (PL) emission efficiencies and strong photoluminescence excitation (PLE) intensity. Compared with the aforementioned samples, the normally used QW sample shows the lowest PL emission efficiencies, the lowest PL emission photon energies and the weakest PLE intensity. In other words, the addition of the InN or InGaN interfacial layers indeed can improve the optical property. Besides, we conduct nanostructure study on five ZnO nanostructure samples including the structures of films, walls and tubes. In the two thin film samples, X-ray diffraction (XRD) measurements reveal the different epitaxial relationships between the ZnO film and the sapphire substrate with different growth temperatures. From the transmission electron microscopy (TEM) images and the diffraction patterns of ZnO walls, we can confirm that a branch of the wall or a tube structure is a single crystal with the same orientation. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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