本論文用光激螢光、時間解析光激螢光與拉曼散射光譜來研究CdTe量子點與重摻雜GaAs的光學特性。由於量子侷限效應,CdTe量子點的光激螢光光譜峰值隨著CdTe的厚度增加往低能量的地方移動。在時間解析光激螢光實驗中,發現4個原子層厚度量子點的光激螢光生命期從13 K到40 K時增加,超過40 K時卻減少。生命期的增加是因為載子從濕層轉移到量子點的緣故,而生命期的減少是因為非輻射效應所引起的。在拉曼散射實驗中發現量子點的拉曼訊號隨著CdTe厚度的增加,其不對稱展寬較不明顯。此結果可用空間相關的模型來解釋。至於重摻雜砷化鎵的光激螢光研究,我們發現其能隙會隨著摻雜濃度增加而減小,與理論預測相符合。在時間解析光激螢光量測中,發現重摻雜的GaAs有載子侷域化的現象。
Optical properties of CdTe quantum dots ( QDs ) and heavily doped GaAs have been investigated using photoluminescence ( PL ) , time-resolved PL , and Raman scattering . Due to the quantum confinement , the PL peak position of QDs shifts to lower energy with increasing the thickness of CdTe thin layer ( the size of QDs ) . With increasing the temperature the decay time of 4 monolayer ( ML ) QDs increases from 13 K to 40 K , then decreases after 40 K . The increase of decay time can be explained by the carrier transfer from wetting layer to the quantum dots , while the decreased decay time is due to the nonradiative effect at high temperature . The asymmetric broadening of Raman peak is found to decrease with increasing the thickness of CdTe layers . This result can be explained according to a spatial correlation model . As for the PL studies of heavily doped GaAs , it is found the band gap of GaAs decreases as the doping concentration increases , in agreement with the theoretical prediction . In addition , the localization of carrier in heavily doped GaAs is demonstrated in the time-resolved PL .