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請使用永久網址來引用或連結此文件:
http://ir.hust.edu.tw/dspace/handle/310993100/1794
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| 題名: | 三五族氮化物成分相關之能隙彎曲函數的探討 |
| 作者: | 劉柏挺 |
| 貢獻者: | 修平技術學院機械工程系 |
| 關鍵詞: | 氮化鋁鎵銦;能隙;彎曲係數 |
| 日期: | 2006-07-01
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| 上傳時間: | 2009-10-28T03:56:31Z
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| 摘要: | 三五族氮化物半導體被視為是最具潛力的光電材料之一，因為它具有優異的光學特性，諸如相當低的介電常數和可調波長涵蓋整個可見光區至部分紫外線和紅外線的 寬範圍能隙，及大部分的氮化物為發光效率較高的直接能隙晶體結構。現今常用的兩種基本氮化物結構一為六方晶系的wurtzite結構(WZ)，另一為立方 晶系的zincblende結構(ZB)。氮化物的WZ結構皆為直接能隙。然而ZB結構也存在著不同於WZ結構的優點，例如ZB結構具有較小的有效質量， 因此能夠提供較大的光學增益，並且降低雷射二極體的臨界電流密度；以及以砷化鎵為基板較容易得到平整鏡面。 對於三元氮化物，一般的研究者以固定的能隙彎曲係數來描述不同濃度下的能隙值。近年來長晶技術有相當大的進步，最近從許多高品質的InN實驗證實，InN 直接能隙值約為0.8 eV且為大家所接受，此值遠低於長久以來物理界認為的1.9 eV，因此三元氮化物的能帶結構與光學特性引起廣泛的探討。「以固定的能隙彎曲係數來描述不同濃度下的能隙值」是否適用於所有的WZ及ZB結構的三元氮化 物是一個值得研究的課題。本研究計畫的理論計算以物理基本原理為基礎，使用國家高速網路與計算中心所提供之CASTEP軟體進一步來探討WZ及ZB結構的 三元氮化物的能隙彎曲係數與化合物組成濃度(x)成函數關係，即b是x函數。研究的結果與之前的研究成果比較，則整個三五族氮化物從二元的AlN，GaN 及InN到四元的AlxGayInzN (x+y+z = 1)的能帶結構、直接能隙、間接能隙、價電帶厚度、直接能隙彎曲係數及間接能隙彎曲係數等物理與光電性質就可完整的建立。;III-nitride semiconductor is recognized as one of the most promising optoelectronic materials, because there are many outstanding optical properties such as lower dielectric permittivity and wide range band gap tuned from the infrared, the visible across the ultraviolet spectral range, and most of the nitride crystal structures have direct energy band gap resulting high emitting performance. Two basic crystal structures of III-nitride semiconductors are used today: hexagonal wurtzite (WZ) structure and cubic zincblende (ZB) structure. Although the WZ structure of III-nitride semiconductor always has direct band gap, the ZB structure still possesses distinct advantages over WZ structure. For example, the ZB structure is provided with larger optical gain and lower threshold current density because of its smaller effective mass, and has mirror facets compatible with substrates such as GaAs. For the ternary nitride alloys, the band gap is generally expressed as a linear combination of the band gap of the two forming binary compounds and a quadratic modified term with a constant coefficient, called bowing parameter. Epitaxial technology has since progressed remarkably. High-quality InN has recently become available and its direct band gap has been determined to be near 0.8 eV, which is much smaller than the 1.9 eV commonly accepted by the physics community in the past few years. Therefore, the band structures and optical characteristics of ternary III-nitride semiconductor have attracted extensive research. It is worth researching subject whether the constant bowing parameter is suitable for the WZ and ZB ternary nitride alloys. In this research project, the calculation based on first principles is performed by using the CASTEP program, provided by the National Center for High-Performance Computing, to further investigate the composition-dependent band-gap bowing function for WZ and ZB III-nitride alloys. Comparing the results obtained from this project with those from my prior research, the physical properties and optical characteristics including band structure, direct band gap, indirect band gap, width of valence band, bowing parameter of direct band gap, and bowing parameter of indirect band gap can be completely set up for the III-nitride alloys from binary alloys, AlN, GaN, and InN, to quaternary alloys AlxGayInzN (x+y+z = 1).;計畫編號:NSC95-2112-M164-001-MY3;研究期間:200808~200907 |
| 顯示於類別: | [機械工程系(含精密機械與製造科技碩士班)] 研究計畫
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