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標題: | 砷化鎵-砷化鋁超晶格電子態之耦合效應 Valley Mixing Effects on Electronic States of GaAs-AlAs Superlattices |
作者: | Fu-Jung Yang 楊富戎 |
指導教授: | 薛文証 |
關鍵字: | 超晶格,砷化鎵/砷化鋁,能谷耦合,共振穿隧,能帶結構,反交叉,傳輸矩陣法, superlattice,GaAs/AlAs,valley mixing,resonant tunneling,band structure,anticrossing,transfer matrix method, |
出版年 : | 2008 |
學位: | 碩士 |
摘要: | 本論文主要的目的在於研究雙能谷耦合對GaAs/AlAs半導體材料的穿隧及能帶結構之影響。我們使用Liu所提出的脈衝函數形式之耦合項來模擬對於X能谷所造成的影響,並以波封函數近似法為基礎,配合傳輸矩陣法推導出共振穿隧與能帶結構之特徵方程式。利用這些推導的結果分析位能障寬度、位能井寬度及耦合變量等參數變化對單位能障與雙位能障的穿隧現象之影響,最後並分析週期性結構超晶格之能帶結構變化。相較於傳統的單能谷問題,我們觀察出能谷耦合不僅會使整體的穿隧機率提升,也因此出現數個極大的峰值,其峰值數量與位能障寬度有關;在能帶結構的部分,能谷耦合會使Γ和X能階在相交處分離,造成兩能階混合的情形,讓原本的能帶位置起了很大的變化。 The main purpose of the thesis is to study the valley mixing effects on transmission and band structure of GaAs/AlAs semiconductors. We simulate the effect of X valley based on envelope function approximation and the coupling term in impulse function form proposed by Liu and derive the eigenfunctions of resonant tunneling and band structure by transfer matrix method. By changing the barrier width, well width and coupling parameter, we simulate single/double barrier tunneling and calculate the variation of band structure of periodic superlattice with above results. Comparing with conventional single-valley problem, we find that valley mixing not only raises the total transmission probability but produces several peaks whose quantities associate with the barrier width. In band structure, the valley mixing will separate the crossing of Γ and X levels and makes the two energy levels mix that shifts the original band location a lot. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/26597 |
全文授權: | 未授權 |
顯示於系所單位: | 工程科學及海洋工程學系 |
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