砷化銦單量子點於垂直電場中之光激螢光

Abstract

本論文以光激發螢光光譜探討砷化銦量子點對垂直電場的響應。量子點內部載子狀態可藉由外加偏壓調變，觀察到如激子(X)、雙激子(XX)和各種帶電的激子複合物的螢光光譜譜線，利用雷射激發功率相依、垂直電場相依以及全角度偏振螢光光譜得以分辨其對應的激子種類。量子侷限史塔克效應也在本論文中量測並探討，在同一顆量子點中，因為載子間的庫倫作用力，雙激子與帶正電激子的史塔克偏移量趨勢不同於激子與帶負電激子。在激子發光能量與電場的關係中，最大的發光能量在非零電場顯示其具有內建的電偶極。統計不同顆量子點的量測結果，電偶極與極化率隨著量子點發光能量上升而下降，此趨勢與已經發表的文獻一致，並且物理機制也在本論文中探討。此外，我們研究外加垂直電場對於量子點的精細結構劈裂量的影響，在被量測的量子點中，其中一個量子點的精細結構劈裂隨外加垂直電場下降而線性減小的趨勢被量測到。

In this thesis, the effect of external electrical field on InAs self-assemble quantum dots (QDs) were investigated by means of single dot photoluminescence (PL). The occupation of the quantum dot can be controlled by varying the external bias between the Schottky gate and the back Ohmic contact so the PL peaks from excitons, biexcitons, and other excitonic complexes were clearly observed and identified by varied excitation power, the external electrical field, and the polarization-resolved emission. The quantum confined Stark’s effect of excitons has been observed and studied. In the same QD, the magnitude and characteristic of the stark shift in XX and X+ is different from that in X and X-, which is attributed to the Coulomb interaction between carriers. From the field dependence of the transition energy, the maximum transition energy occurs at a nonzero electrical field, which revealed a nonzero built-in dipole moment in QDs. The dipole moment and polarizability decrease with increasing transition energy, which is consistent with other reported works and its physical reason has been discussed here. Furthermore, we have investigated the vertical electrical field effect on fine structure splitting (FSS) in QDs. One of the studied QDs shows a clear trend that the FSS decreases linearly with the decreasing electrical field.