稀磁性半導體硒化錳鋅磊晶層包覆碲化鋅量子點之分子束磊晶與其物性研究

Molecular Beam Epitaxy and Physical Properties of ZnTe Quantum Dots Embedded in the Diluted Magnetic Semiconductor ZnMnSe

邱繼淳(Chi-Chun Chiu)

指導教授 ： 王智祥 ； 周武清

中原大學/理學院/應用物理研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500315

摘要

利用分子束磊晶技術在三元化合物半導體硒化錳鋅上成長二元碲化鋅自聚性量子點結構，以反射式高能電子繞射裝置與原子力顯微鏡觀察量子點形成過程，並且利用光激螢光量測其光學特性。
由反射式高能電子繞射條紋可以看出，在去氧化完成與成長完硒化錳鋅緩衝層後的反射式高能電子繞射條紋呈現線狀，並且出現2×1的晶格重構圖案，反映出此結構是以二維的長晶模式成長，鋪上平均覆蓋厚度分別為1.8、2.0、2.2、2.4、2.7與3.0原子層之碲化鋅後，2×1晶格重構線條逐漸隨著平均覆蓋厚度增加而成為點狀，點的寬度也逐漸增加，証明三維的碲化鋅自聚性量子點結構已逐漸形成。研究此套樣品的低溫光激螢光譜時發現，譜峰的能量值在2.3 電子伏特的光激螢光是來自硒化錳鋅緩衝層，譜峰的能量值介於1.88 電子伏特到2.19電子伏特的光激螢光則是發自碲化鋅自聚性量子點，隨著覆蓋層的厚度增加，訊號有紅位移的趨勢，伴隨著半寬縮小。另外從不同溫度的光激螢光實驗可以得知，隨著溫度升高訊號有紅位移的趨勢並伴隨著半寬的增加，利用活化能的經驗公式模擬可以知道碲化鋅量子點的活化能約數十毫電子伏特。再利用瓦希尼(Varshni)經驗公式對變溫光激螢光數據做擬合，可以得到聲子能量的相關參數。

關鍵字

原子力顯微鏡 ； 光激螢光 ； 分子束磊晶 ； 碲化鋅量子點 ； 硒化錳鋅 ； 反射式電子繞射

並列摘要

ZnTe self-assembled quantum dots (QDs) embedded in ZnMnSe matrix on the GaAs (001) substrate were grown by molecular beam epitaxy (MBE). The reflection high energy electron diffraction (RHEED) and the atomic force microscopy (AFM) were used to investigate the processes of QD formation. The optical properties were also studied by the photoluminescence (PL) measurement.
As the desorption and growth of ZnMnSe buffer layer were finished, a streaky RHEED pattern of the 2×1 crystal reconstruction was observed. It implies a two-dimensional (2-D) growth. However, after different coverages, 1.8, 2.0, 2.2, 2.4, 2.7, and 3.0 monolayers (MLs),of ZnTe layer were deposited on the ZnMnSe buffer layer, the streaky pattern gradually turned to spotty pattern. It reflects the growth process transfers from the 2-D growth mode to three-dimension (3-D) growth mode.
The PL peak situates at 2.25 eV is from the emission of rough ZnMnSe buffer. Whereas, the PL peak at energy range from 1.88 eV to 2.19 eV is from the ZnTe QDs emission. Furthermore, the red shift and the reduction of the full width at half maximum (FWHM) were enhanced with the increasing of the ZnTe QDs coverage. As the temperature is increased, a red shift of the PL peak and the line-width broadening were observed in the temperature dependent PL spectra. By using the fitting formula of activation energy, the activation energies (Ea) of the ZnTe QDs samples were obtained. Varshni relation is also used to fit the temperature dependent PL peak position. The phonon energy related fitting parameters were obtained.

並列關鍵字

RHEED ； photoluminscence ； ZnMnSe ； Molecular Beam Epitaxy ； AFM ； ZnTe quantum dot

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