以化學束磊晶法成長三族氮化物奈米結構; III-nitride Nanostructures Grown by Chemical-Beam Epitaxy

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题名:	以化學束磊晶法成長三族氮化物奈米結構;III-nitride Nanostructures Grown by Chemical-Beam Epitaxy
作者:	趙志剛;Chih-Kang Chao
贡献者:	電機工程研究所
关键词:	化學束磊晶系統;奈米結構;氮化鎵;氮化銦;nanostructures;indium nitride;gallium nitride;chemical beam epitaxy
日期:	2006-07-08
上传时间:	2009-09-22 11:37:30 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	此篇論文的內容包括設計及製作化學束磊晶系統、以自製的化學束磊晶系統成長氮化鎵及氮化銦奈米柱，以及氮化銦奈米柱的光學特性分析。自製化學束磊晶系統的重點在於以低成本完成在超高真空環境中，能夠以高溫成長高品質的三族氮化物半導體。三軸式的基板傳動升降裝置，能夠提供穩定的旋轉，並可依需求微調垂直角度，具有相當好的擴充性。氮氣電漿源提供了極有效率的五族來源，對於需要於低溫成長的特定材料，例如氮化銦，可以提供適合的成長環境。三族有機金屬氣體，經由特製的氣環導入成長腔體，可以使反應物有效的達到基板表面，能夠提升成長速率，並節省原料。熱源模組經由適當的材料選擇及加工，可以將能量聚集到成長區，以達到高溫的成長需求。整體的熱阻絕設計，可以保護熱區周圍的配件，以使系統穩定工作。利用自製的化學束磊晶系統，可以於c方向的藍寶石基板上，成長幾乎無缺陷的氮化鎵奈米柱。和大部分奈米結構成長條件不同的是，成長高品質垂直於表面並獨立的氮化鎵奈米柱，不需要金屬作為觸媒，顯示該化學束磊晶系統非常適於成長奈米結構。除了氮化鎵奈米柱之外，該系統也可以在沒有觸媒的條件下，於藍寶石基板上成長氮化銦奈米柱。這些奈米柱幾乎都垂直基板表面，沿著同一方向成長，隨著三甲基銦對氮氣的流量比由0.4到0.7，奈米柱的直徑由20奈米到40奈米。X射線繞射儀以及穿透式電子顯微鏡的檢測結果可以判斷，這些奈米柱都是偏好沿著c軸成長的單晶相六方最密堆積晶體。拉曼光譜可以看到僅有二個和氮化銦相關的訊號 (high) 以及 (LO) 顯現，表示奈米柱的結晶品質相當優良。氮化銦奈米柱的光學性質，利用光激螢光光譜(PL)以及拉曼光譜進行量測。光激光譜的峰值，隨著奈米柱的直徑由40奈米降到5奈米，而由0.69電子伏特藍移至0.79電子伏特。而拉曼光譜分別於491 cm-1 及 593 cm-1至觀察到 (high) 以及 (LO)活性聲子模態，但是這兩個模態的位置並不隨著奈米柱直徑尺寸的變化而變，顯示奈米柱中的殘餘應力以及載子濃度，並不跟隨奈米柱的尺寸而變。也就是說，應力效應和Moss-Burstein效應，在這個實驗中，對於PL光譜的峰值變化，並沒有產生影響力。將光激光譜的變化與藉由依據有限位能井模型進行的理論計算進行比對，可以發現，光譜的峰值變化，極有可能是因於奈米柱尺寸變化產生的量子侷限效應。 This dissertation includes the self-designed home-made chemical-beam epitaxy system, the methods of synthesizing gallium nitride nanorods and indium nitride nanorods without catalyst, and the discussion of detailed optical properties of indium nitride nanorods. The chemical-beam epitaxy can be work in high vacuum circumstances at high temperature with low fabrication cost. Three-axle z-axis manipulator provides stable rotation capability and flexible expansibility. The design of heat module is able to work at high temperature up to 1100oC without harming the surrounding components. Group-V source is supplied by nitrogen plasma, which is beneficial for indium nitride growth. Group-III metalorganic sources are introduced into the growth chamber by a special designed gas source ring, which makes the reactants hinge on the substrate surface efficiently and uniformly. The growth of dislocation free GaN nanorods on c-sapphire substrates by a CBE technique is demonstrated. By compared the CBE method with other common growth methods, the CBE is a more feasible technique to fabricate high-quality, high-density, and vertical-alignment GaN nanorods. Without extra metal catalyst required, the thickness and length distributions of each GaN nanorods were formed identically. Furthermore, the nanorods were grown epitaxially and were elongated in the direction parallel to the surface normal. In addition, the InN nanorods were prepared using the same chemical-beam epitaxy without a catalyst. The nanorods are grown nearly unidirectionally with diameters ranging from 20 nm to 40 nm, depending on the In/N flow ratio between 0.4 and 0.7. XRD and TEM results show that these InN nanorods are single phase wurtzite crystals with preferred orientation along the c-axis. Raman spectrum reveals two clear peaks, which correspond to the (high) and (LO) modes, respectively. The optical properties of InN nanorods was followed investigated by using PL measurement and Raman spectroscopy. The emission peaks of PL spectra range from 0.69 to 0.79 eV, showing a blue shift as the rod size decreases from 40 to 5 nm. The Raman spectra of the nanorods exhibit only two active phonon modes, i.e. (high) and (LO), at 491 cm-1 and 593 cm-1, respectively. These two peaks do not shift with rod size, indicating the residual strain as well as the carrier concentration in the nanorods of different sizes is about the same. That obviates the influences of strain and the Moss-Burstein effects on spectral shifts. On the other hand, theoretical calculation based on a finite depth square well model reveals the possibility of quantum size effect on the observed size-dependent PL shifts.
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