碲化錳鋅／硒化鋅量子點之錳摻雜調控與光學特性

Abstract

在砷化鎵基板上利用分子束磊晶成長硒化鋅做為緩衝層，並且於硒化鋅上成長不同沉積時間之碲化鋅零維量子點，在低溫光致螢光光譜下，沉積時間少於2.5層(相當於沉積時間為62.5秒)時會有兩個峰值表現，較高的能量峰值是為二維量子井的貢獻；而較低的能量鋒值則是來自零維量子點的發光。當沉積時間增加到3.0層(75.0秒)以上時只會有單一峰值出現，可單純將其視為零維量子點的貢獻。 之後再以3.0層非磁性的碲化鋅/硒化鋅量子點樣品為基礎，加上控制錳摻雜的時間來製備3.0層碲化錳鋅/硒化鋅量子點，想藉由減少錳元素在摻雜的時間來達到稀釋量子點中的錳元素摻雜的目的，其中錳元素摻雜時間分成0秒，25秒，50秒及75秒。在時間解析光譜下，可觀察到當錳元素的摻雜時間從75.0秒減少至25.0秒時，磁極化子的形成能量也從90毫電子伏特降至24毫電子伏特，且形成所需的時間也從32.8奈秒上升至84.0奈秒，由此可知隨著摻雜時間減少磁化子的影響也隨之減少，但依然可見磁化子的影響，且確認此方法確實能達到錳元素在量子點中稀釋的效果。

ZnTe quantum dots (QDs) were grown on GaAs substrates with ZnSe buffer layer and ZnSe capping layer by molecular beam epitaxy (MBE) system. If the deposit thickness is less than 2.5MLs (equivalent growth time of 62.5 seconds), two peaks were observed in the photoluminescence (PL) spectra. The higher energy peak is contributed from the emission of 2-D quantum well (QW). The lower energy peak is due to the emission from the ZnTe QDs. When the deposit thickness is more than 3.0MLs (75.0 seconds), only the peak from QDs was investigated. Based on the growth conditions of non-magnetic ZnTe/ZnSe QDs of 3.0MLs, the growth and control of Mn doping of 3.0MLs ZnMnTe/ZnSe QDs were studied. The dilution of Mn concentration in the ZnMnTe QDs could be manipulated by the deposition time of Mn. The Mn deposit time was controlled from 0, 25.0, 50.0 to 75.0 seconds. By using the time-resolved PL, the formation of magnetic polarons can be observed for all samples. When the doping time was decreased from 75.0 seconds to 25.0 seconds, the magnetic polarons formation energy decreased from 90meV to 24meV and the magnetic polarons formation time increased from 32.8ns to 84.0ns. The Mn concentration can be successfully diluted in QDs by this way.