臺灣博碩士論文加值系統

在本論文中，我們藉由變溫及變功率光激光譜的量測，對自聚性砷化銦/砷化鎵量子點異質結構的載子遷移特性，做系統性的分析與討論。
利用有機金屬化學氣相磊晶系統所成長的砷化銦量子點樣品，由於在磊晶過程中，採用不同的成長中斷時間(growth interruption time)，故使得二片樣品在量子點的大小、均勻度及密度上，均有所差異。配合變溫光激光譜的量測結果，我們發現光譜的半高寬及發光峰值能量，與樣品的成長中斷時間有密切的關係。成長中斷時間較短的樣品，由於均勻度較差，其光激光譜的半高寬隨著溫度的上升，而有明顯的下降趨勢，同時伴隨峰值的快速紅移。這是由於載子有足夠熱動能脫離量子點的束縛，經由濕層(wetting layer)做載子的重新分佈。當溫度持續升高，電子與聲子散射(electron–phonon scattering)效應逐漸明顯，使得光激光譜的半高寬又開始增加，峰值快速紅移的現象也略趨緩和。對於成長中斷時間較長的樣品來講，由於其均勻度較佳，所以在變溫的光激光譜量測中，我們並未發現半高寬隨溫度上升而有下降的趨勢，這是因為載子重新分佈效應對一個均勻度佳的樣品來講，其顯示出來的效果並不明顯，所以我們只能觀察到電子與聲子散射效應所表現出來的現象，也就是半高寬隨溫度上升而緩慢增加。
在變功率的光激光譜量測中，我們可更進一步解釋量子點載子遷移與能態密度的關係。在低入射功率時，由於量子點能態被佔據的比率較低，使得載子重新分佈效應更加明顯。當入射功率越低，半高寬的最低點也越小，而且峰值的紅移量也越大。從變溫與變功率的光激光譜量測與分析中，我們可以更深入了解量子點結構的載子遷移機制，並進而設計出更佳的元件。

In this thesis, we have systematically investigated the carriers transferring characteristics of self-assembled InAs/GaAs quantum dot (QD) heterostructures through the measurements of temperature-dependent and power-dependent photoluminescence (PL).
The InAs QDs samples were carried out by metal-organic chemical vapor deposition system. The dot density, and dot size uniformity of the samples are different because of their different growth interruption (GI) time during the growth process. According to the measured results, we identify that the full width at half maximum (FWHM) and the peak energy of PL spectra are highly related to the GI time of InAs samples. For the sample with shorter GI time, thanks to the lower dot size uniformity, the FWHM decreases apparently with temperature, accompanied by a quick redshift of the peak energy. It is attributed to the carriers thermally activate outside the dots and redistribute among dots via the wetting layer. As the temperature increases further, the FWHM increases and quick-redshift of peak energy slows down because the electron-phonon scattering becomes important. For sample with longer GI time, which resulting in the better uniformity of this sample, the unusual decrease of FWHM is not observed in the measurement of the temperature dependent PL spectra. Considering the better uniformity of the sample, the effect of carrier redistribution on PL spectra is unapparent. Therefore, the FWHM increases gradually with temperature.
In the measurement of power-dependent PL spectra, the correlation between the carriers transferring and density of state (DOS) in QDs are discussed in depth. With lower incident excitation power, the lower filled portion of DOS leading to the evident carrier redistribution effect in QDs, thus the decrease of FWHM and the redshift of peak energy both increase with decreasing incident power. According to the measurement and analysis of the temperature-dependent and power-dependent PL spectra, the carriers transferring mechanism of QDs heterostructures is well explained and is expected to improve the design of optoelectronic devices.

中文摘要...................................................i
英文摘要.................................................iii
目錄 ..................................................vi
圖目錄 ................................................viii
表目錄 ...................................................x
第一章 緒論...............................................1
1.1 概述...............................................1
1.2 研究動機............................................3
第二章 基本原理............................................4
2.1 量子點特性..........................................4
2.2 量子點成長機制.......................................5
2.3 文獻探討............................................6
第三章 實驗步驟與方法......................................11
3.1 樣品介紹...........................................11
3.2 光激發光原理........................................11
3.3 光激發光(Photoluminescence,PL)量測系統儀器設備介紹....12
第四章 實驗結果與討論......................................17
4.1 低溫光激光譜分析.....................................17
4.2 變溫光激光譜分析.....................................18
4.2-1 變溫光激光譜半高寬分析................................18
4.2-2 變溫光激光譜放光峰值分析...............................19
4.3 變功率光激光譜分析....................................21
4.3-1 變功率光激光譜半高寬分析...............................21
4.3-2 變功率光激光譜放光峰值分析.............................22
第五章 結論................................................39
參考文獻....................................................43
作者簡介....................................................47

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