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標題: | 銻砷化鎵應力緩衝層對砷化銦鎵量子點結構光學特性之研究 Optical Properties of InGaAs Quantum Dots with GaAsSb Strain Reducing Layers |
作者: | Han-Yun Jhang 張瀚允 |
指導教授: | 郭茂坤(Mao-Kuen Kuo) |
關鍵字: | 量子點,應力緩衝層,有限元素法, quantum dot,GaAsSb,strain reducing layer,finite element method, |
出版年 : | 2012 |
學位: | 碩士 |
摘要: | 本文旨在研究銻砷化鎵應力緩衝層對砷化銦鎵量子點結構光電性質之影響。文中以線性彈性力學與k•p理論,配合有限元素法估算量子點形狀、材料濃度,以及緩衝層對於量子點結構與光電性質之效應。
研究發現銻砷化鎵應力緩衝層將可降低量子點結構之應變量。而當緩衝層厚度高於量子點高度,量子點結構之應變減少量較大,並以緩衝層完全包覆量子點之應變減少量最大。緩衝層厚度與磊晶順序也將影響量子點結構之光電性質。當緩衝層厚度不及量子點高度,量子點幾何結構與其材料濃度對於量子點光電性質影響甚鉅。數值結果顯示,銻濃度高於16%,量子點由第一型結構轉變至第二型結構,而能量紅移現象也將隨著銻濃度之增加而變大。 本文亦發現,使用砷化鋁鎵材料包覆量子點結構,將可增加結構之量子侷限效應。隨著量子點尺寸增加,侷限在量子點電子能態之數量有增加趨勢,並以量子點高度變化對量子點結構光電性質影響最為敏感。當量子點高度過高時,電子及電洞波函數重疊率將減少,而量子點銦濃度高者維持高光學增益之量子點高度容許範圍較小。 The optical properties of InGaAs quantum dots are investigated. A model based on linear elasticity and k•p theory is developed to analyze the effect of shapes and composition concentrations of quantum dot, as well as GaAsSb strain reducing layers on optical properties of the InGaAs quantum dots by means of finite-element method. The numerical results show that GaAsSb layers can release the strain field inside and in the neighborhood of InGaAs quantum dots. When the thickness of GaAsSb layer is greater than the height of quantum dot, the strain relaxation is higher. Moreover, by using GaAsSb as buffer and capping layer simultaneously, strain will be released most. Both GaAsSb layer thickness and the order of epitaxy will influence the optical properties, and the effect are more obvious when the thickness of GaAsSb strain reducing layer is less than the quantum-dot height. For Sb content > 0.16, the transition way of the quantum dot transfers from type I to type II, and the red-shift of transition energy increases as Sb content increases. The calculated results also indicate that the AlGaAs layer can increase quantum confinement. The number of electron-energy-state confined in the quantum dot increases as the quantum dot size increases, and optical properties are more sensitive to the quantum-dot height. Excessively high quantum dot causes the wave-function overlaps to decrease. For high indium concentration quantum dots, the range of quantum-dot size with high optical gain is narrow. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65082 |
全文授權: | 有償授權 |
顯示於系所單位: | 應用力學研究所 |
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