Transmission Electron Microscopy Studies of InGaN/GaNMultiple Quantum Well Nano-Structures of Different SiliconDoping Conditions
| Autor: | Meng-Ku Chen, 陳孟谷 |
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| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 In this research, we have investigated the nanostructures of InGaN/GaN multiple quantum wells (MQWs) with different indium concentrations, different silicon doping regions, and different silicon doping concentrations. We also studied the effects of post-growth thermal annealing and electron beam exposure on the nanostructure. The methods used for studying our samples, including material and optical analysis methods. Material analysis methods include high-resolution transmission electron microscopy (HRTEM) and the strain-state analysis (SSA). Optical analysis methods include photoluminescence (PL) and photoluminescence excitation (PLE). From strain-state analysis (SSA) results, we could clearly see the differences of nanostructures between the samples of different doping conditions. Typically, more clusters were formed in Si-doped samples, particularly in the barrier-doped sample. Also, more clusters can be formed by increasing silicon doping concentration. Optical measurements showed that with Si-doping, the recombination efficiency could be improved. Such an improvement could be attributed to stronger carrier localization (more clusters formed) and better strain relaxation (weaker quantum-confined stark effect) upon silicon doping, particularly doping in barriers. We have observed that thermal annealing could change the nanostructures and optical properties of InGaN/GaN MQWs. We have found that electron beam exposure for a few minutes may not change the nano-structure of an InGaN/GaN QW sample. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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