以不同位置的錳摻雜調控碲化鋅／硒化鋅量子點磁極化子形成機制

Abstract

本論文利用分子束磊晶系統在砷化鎵(001)基板上成長4.4原子層厚的第二型能帶結構碲化錳鋅/硒化鋅量子點，藉由錳元素不同的摻雜層數與摻雜位置，調控整體碲化錳鋅/硒化鋅量子點內錳磁性離子濃度。並利用光激螢光光譜與時間解析光譜觀察束縛磁極化子的形成機制與變化，由時間演進光激螢光光譜峰值的位移量對時間的關係結果顯示，0奈秒時有兩組光譜峰值訊號的產生。隨著時間的演進，位於高能量峰值位置的訊號貢獻會逐漸降低，並約30奈秒後由低能量峰值位置所主導。隨著錳元素摻雜層數的減少，低能量峰值位置隨時間演進並無明顯紅移，亦即無明顯磁極化現象，而驗證能將束縛磁極化子的影響效應降至最低。時間演進光激螢光光譜進一步證明調控不同錳元素的摻雜位置亦能影響整體束縛磁極化子的形成，除了透過不同位置的錳摻雜可調控磁極化子形成機制亦可降低錳離子於量子點的數量。

Type-II ZnMnTe/ZnSe quantum dots (QDs) of 4.4 monolayers were grown on (001) GaAs substrates by Molecular Beam Epitaxy (MBE). With different Mn doping layers and doping position, the concentration of Mn magnetic ions within ZnMnTe/ZnSe QDs could be controlled. Time-resolved photoluminescence (TRPL) spectroscopy was employed to analyze the formation mechanism and behavior of bounded magnetic polaron (BMP). Based on the fitting results of peak shift versus decay time, two peaks were observed in the spectrum at the time of 0 ns. The peak at higher energy decreased in emission intensity abruptly and the peak at lower energy dominated after the time of 30 ns. The red shift of the lower energy is not pronounced. It implies weak BMP effect and illustrates that the effect of BMP was minimized as Mn doping layer decreased. The TRPL results further shows that the BMP effect also could be manipulated by varying the Mn doping positions. The control of the formation mechanism of BMP as well as the dilution of Mn concentration in the quantum dots could be achieved by different Mn doping position.