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標題: | 以分子束磊晶法成長(100)與(111)方向砷銻化鎵/砷化鎵材料之結構與特性研究 Study of structural properties and characterization of (100) and (111) GaAsSb/GaAs grown by molecular beam epitaxy |
作者: | Yi-Ren Chen 陳奕任 |
指導教授: | 楊英杰 |
關鍵字: | 分子束磊晶,半導體III-V材料,相分離,正規溶液模型,砷銻化鎵,差排,微雙晶與複合雙晶, Molecular beam epitaxy,Semiconducting III-V materials,phase separation,regular solution model,GaAsSb,(111)B GaAsSb,dislocations,twins,double twins, |
出版年 : | 2012 |
學位: | 博士 |
摘要: | 本論文利用氣態源分子束磊晶於不同溫度下成長砷銻化鎵塊材於(100)與(111)B面之砷化鎵基板。分別研究樣品成長於不同基板方向之相分離現象與結構特性。首先,我們提出一單原子層正規溶液模型(monolayer regular solution model),考慮砷銻化鎵塊材表面單層原子之自由能,以解釋相分離與成長方向之相依性。在此模型中,只有座落於同一層原子之次鄰近原子對相互作用參數(interaction parameter)有影響。因此,對於(111)B 和(100)方向成長之砷銻化鎵薄膜,其相互作用參數將分別修正成omega/2和omega/3,在此omega表示砷銻化鎵塊材之相互作用參數。考慮形變(strain)修正後,此模型可成功解釋(111)B 和(100)方向砷銻化鎵之互溶間隙(miscibility gap)現象。
第二,我們利用穿透式電子顯微鏡與高解析度X光繞射儀來分析於不同溫度下成長之(100)與(111)B砷銻化鎵薄膜其結構與特性。當樣品成長溫度低於525度且表面呈現 (2×2)重構,我們觀察到雙晶(twin)與複合雙晶(double twin)共存於樣品中。穿透式電子顯微鏡顯示複合雙晶與基板之接合處及複合雙晶與不同平面所形成之雙晶接合處,原子鍵有著高度扭曲(distorted)失真。後者所造成之原子扭曲將延伸至表面並造成表面類似金字塔結構。除了穿透式電子顯微鏡之外,X光繞射儀ϕ角掃瞄(phi scan)亦用來量化此雙晶缺陷密度,利用量測雙晶缺陷所造成之額外(220)晶面。當樣品成長溫度於550度且表面重構由(2×2)轉換至(√19×√19),樣品內之雙晶缺陷密度將大幅度降低,且高解析穿透式電子顯微鏡顯示此樣品之主要缺陷將轉變為差排缺陷(misfit dislocations)。於(2×2)和(√19×√19)表面重構下成長之(111)砷銻化鎵薄膜,其主要應力釋放(stress-relief)機制分別為微雙晶與差排缺陷,且此兩種表面重構將導致後續成長之砷銻化鎵薄膜形成三維島狀(3-D island)與三角交錯(triangular-hatched)之地貌。 In this dissertation, GaAsSb epilayers are grown on (100) and (111)B GaAs substrates with different growth temperature using gas source molecular beam epitaxy (GSMBE). Orientation-dependent phase separation and structural properties of grown samples were studied in this work. Firstly, we propose a monolayer regular solution model considering the free energy of the surface monolayer to explain the orientation-dependent phase separation in GaAsSb. In this model, only the interaction between the second nearest-neighboring atoms sitting on the same monolayer contributes to the interaction parameter. As a result, the parameter reduces to omega/2 and omega/3 for (111)B GaAsSb and (100) GaAsSb, where omega is the parameter of bulk GaAsSb. With the inclusion of strain effect, this model well explains the immiscibility behavior of (111)B GaAsSb and (100) GaAsSb. Secondly, structural properties of (100) and (111)B GaAsSb with different growth temperature were studied using transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXRD). We observed twins, double twin in samples grown at a temperature lower than 525ºC with (2×2) surface reconstruction. Lattice image of cross-sectional TEM shows strong disorders existing at the interfaces where the double twin, formed in the primary twin with respect to (111)B mirror plane, joints the bulk or twins with respect to other {111} plane. The disorder resulting from the latter joint is able to extend to the surface, leading to pyramid surface structure. Phi-scan XRD was used to quantify the twin density by measuring the additional (220) peaks resulting from the twins. As the growth temperature increases to 550ºC with (√19×√19) surface reconstruction, twin density drastically decreases. Cross-sectional TEM shows only misfit dislocations along the growth plane. The major stress-relief mechanism for (111)B GaAsSb grown under (2×2) and (√19×√19) phase are micro twins and misfit dislocations, respectively. Also, these two surface conditions correspond to the subsequent surface morphology of 3-D island and triangular-hatched accordingly. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/16072 |
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顯示於系所單位: | 電子工程學研究所 |
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