| Summary: | 碩士 === 國立交通大學 === 電子物理系 === 91 === We have studied optical properties of AlGaN films grown by metal organic chemical vapor phase epitaxy under various ammonia flow rate. From micro-photoluminescence (Micro-PL) spectra, there is an extra peak in the V-defect, which is 0.1 eV lower than the near band edge emission. The origin of this extra peak is the defect band induced by V-defect. In order to determine the characteristics of Inbe, and IV, the excitation power dependent measurements were carried out indicating that they are not from donor-acceptor pair (DAP) transitions. Furthermore, the temperature dependence of Micro-PL was studied and the S-shape behavior was observed in the spectrum as due to the spatial fluctuation, for instance, Ga vacancy formed localized states. For Al0.9Ga0.91N, the activation energy of 27.8 meV and the exciton localization energy of 6.1 meV film for Inbe were obtained from the Arrhenius plot. However, for IV, the activation energy increases to 65.1 meV and the localization energy increases to 7.6 meV. By using the photoluminescence excitation (PLE) technique, we found that the V-defect created new energy levels that are responsible for the new IV emissions. We suggested that the broad band from the V-defect is probably related to acceptor-like level due to Ga vacancy.
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