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Title: | 烏采結構氮化銦鎵量子點光學性質之研究 Optical Properties of Wurtzite InGaN/GaN Quantum Dots |
Authors: | Kuo-Bin Hong 洪國彬 |
Advisor: | 郭茂坤 |
Keyword: | 氮化銦鎵,量子點,壓電力學,四能帶k.p漢彌爾頓,有限元素法, InGaN,quantum dots,piezoelectricity,four-band k.p Hamiltonian,finite element method, |
Publication Year : | 2010 |
Degree: | 博士 |
Abstract: | 本文旨在研究烏采結構氮化銦鎵/氮化鎵量子點結構的光學性質。文中以線性壓電力學理論與四能帶k.p漢彌爾頓,配合有限元素法軟體—COMSOL Multiphysics分析自組式氮化銦鎵量子點的大小、形狀、銦濃度及濕潤層厚度等對機電場之影響,進而探討氮化銦鎵量子點結構的光學性質。
本文內容包含全耦合壓電力學模型與半耦合壓電力學模型之比較、正負剪力壓電常數的比較、濕潤層對量子點光學性質的影響及改變氮化鎵基板的晶體角度,探討量子點成長於不同晶體角度之基板時其光學性質的變化,同時針對量子點的底部寬度、頂部寬度、高度、濕潤層厚度及銦濃度等因素加以分析,以了解這些參數在任意晶體角度下的影響程度。 數值結果清楚顯示,分析三族氮化物半導體量子點結構的機電場與光學性質時,使用全耦合壓電模型較為適合,而剪力壓電常數的正負號在計算量子點結構的光學性質時,扮演一個重要的角色。同時,若要準確分析量子點結構的壓電位能與光學性質,濕潤層的厚度與銦濃度必須加以考慮。最後,不論量子點的尺寸、形狀、銦濃度及濕潤層厚度,當量子點成長於晶體角度為70度至75度之間的氮化鎵基板時,將會有最大的波函數重疊量,且躍遷能量得以大幅提升。故,本文所分析的結果,可作為量子點光學元件設計時的參考依據,以提升元件的效能。 The aim of this article is to investigate the optical properties of wurtzite InGaN quantum dots (QDs) grown on GaN substrates with arbitrary crystal orientation. The fully-coupled piezoelectric model and four-band k.p Hamiltonian are developed to analyze the effects of size, shape, composition, and wetting layer (WL) on the electromechanical fields and optical properties. Moreover, the electromechanical equations and Hamiltonian for arbitrary crystal orientation can be derived from the coordinate transformation. Numerical results revealed that the fully coupled piezoelectric model for calculating the electromechanical fields and optical properties of InGaN QDs may be more appropriate. And then the sign of shear piezoelectric constant seems to play an important role in the piezoelectric potential and optical properties. In addition, it is important that the thickness and indium composition of the WL should be considered in the numerical analysis. On the other hand, we found that the transition energy and electron-hole overlap will be effectively raised when the QDs grown on semipolar or nonpolar substrates and the greatest increase in wave function overlap occurs at θ=70º-75º, regardless of the size, shape, composition of QDs, and the thickness of WL. We concluded that QDs grown on semipolar substrate should effectively improve the performance of optical devices, especially for crystal angle is between the 70º and 75º. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/10584 |
Fulltext Rights: | 同意授權(全球公開) |
Appears in Collections: | 應用力學研究所 |
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ntu-99-1.pdf | 4.23 MB | Adobe PDF | View/Open |
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