標題: 氮化鎵薄膜表面V 型缺陷結構之微拉曼光譜研究
Studies of V-defects on GaN Films by Micro Raman Spectroscopy
作者: 沈承勳
Chern-Hsun Shen
李明知
Ming-Chih Lee
電子物理系所
關鍵字: V型缺陷;拉曼光譜;氮化鎵;禁止模態;聲子電漿耦合;線差排密度;V-defect;Raman;GaN;forbidden mode;phonon-plasmon;dislocation density
公開日期: 2004
摘要: 在本論文中,我們利用原子力顯微鏡(AFM)、微拉曼光譜(micro-Raman)等方法研究利用金屬有機化學氣相磊晶系統(MOCVD)所成長的氮化鎵薄膜表面上的V型缺陷。在微拉曼光譜分析中,發現在不同摻雜濃度n型氮化鎵薄膜上直徑3.3微米的V型缺陷內,其LO相關的模態相對於平坦處都有明顯的藍移情形。而在同樣摻雜濃度下、不同大小的V型缺陷中,隨著V型缺陷的直徑增加,禁止模態(forbidden modes) A1(TO)、E1(TO)強度增加,而LO相關的模態則有明顯的藍移行為。我們將禁止模態的出現歸因於表面形貌的改變而提供了側向散射,而LO相關模態的藍移則是由於V型缺陷下方較高的線差排密度(dislocation density)提供了許多的電子。經由LO聲子-電漿的耦合模型(LO phonon-plasmon coupling)以及有效電子濃度(effective electron density)計算,我們推測在V型缺陷中心下方的線差排密度數量級在1010cm-2以上。
The optical properties of V-defects on GaN films were characterized by using atomic force microscopy and micro-Raman spectroscopy. Raman LO related modes of 3.3□m V-defects show noticeable blue shifts from different doping concentration samples. For V-defects of different size, the appearance of forbidden Raman modes A1(TO) and E1(TO) inside V-defects is due to the right angle scattering from morphology variation. Distinct blue shift of LO related modes was also observed inside V-defects compare to the plain region, especially in large V-defects. Simulation results obtained from the phonon-plasmon interaction model suggest a higher carrier density inside V-defects than that on the plain region. Thus, we deduced a higher dislocation density (~1010cm-2) inside V-defects than that (108~109cm-2) on the plain by considering effective electron density.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009221554
http://hdl.handle.net/11536/76157
Appears in Collections:Thesis


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