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標題: 以MOCVD成長氧化鋅磊晶膜及其特性之研究
Growth and Characterization of ZnO Epilayers Using MOCVD
作者: 林伯融
Lin, Po-Rung
關鍵字: MOCVD
buffer layers
出版社: 材料工程學系所
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摘要: 本實驗利用垂直式有機金屬化學氣相沈積成長氧化鋅磊晶膜於(001)面之藍寶石基板上。分別利用二乙基鋅(DEZn)與99.999%高純度的氧氣作為鋅與氧的來源。本篇論文分兩部份: (一)緩衝層對氧化鋅磊晶膜特性之影響 、(二)退火處理對氧化鋅磊晶膜之影響。由第一部份實驗結果得知加入400℃緩衝層之氧化鋅磊晶膜相較於不加緩衝層於500℃直接成長於藍寶石基板上之氧化鋅磊晶膜,400℃緩衝層之加入並不會提升第二層氧化鋅磊晶膜之結晶性、電特性與光激發特性。加入450℃緩衝層之氧化鋅磊晶膜可以得到X光繞射峰半高寬為0.25°、載子濃度為2.45×1018 cm-3、載子遷移率為71 cm2/V-s、室溫光激發光譜峰值半高寬為14 nm之結果,相較於不加緩衝層於500℃直接成長於藍寶石基板上之氧化鋅磊晶膜,450℃緩衝層之加入能提升第二層氧化鋅磊晶膜之結晶性、電特性與光激發特性。 第二部份將450℃直接成長於藍寶石基板之氧化鋅磊晶膜(表面粗糙度為15 nm、X光繞射峰半高寬為0.53°、載子濃度為6.63×1018 cm-3、載子遷移率為60 cm2/V-s)於不同溫度(700~1000℃)分別在氮氣、空氣、氧氣中退火。由結果得知氧化鋅磊晶膜在氮氣環境中退火可以使表面粗糙度降低為1 nm,X光繞射峰半高寬降低為0.35°。氧化鋅磊晶膜在氧氣環境中退火可以降低載子濃度為1.75×1018 cm-3且提升載子遷移率為94 cm2/V-s。由光激發光譜其近能帶發光與深層發光的強度比值結果得知,在氮氣環境中退火其強度變化與氮原子置換氧原子之缺陷的增加與氧空缺增加有關,在氧氣環境中退火其近能帶發光與深層發光的強度比值變化與氫雜質原子和鋅空缺增加與鋅間隙原子減少有關。
Zinc oxide (ZnO) is a wide band-gap semiconductor with an energy gap of 3.37eV and large exciton binding energy (60meV). It has high potential for emitter applications in the blue to ultraviolet region. In this thesis, the ZnO epilayers were grown on sapphire c-plane (0001) substrates using a vertical MOCVD system. Diethylzinc and high-purity oxygen gas were used as source chemicals and Ar as the carrier gas. There are two parts in this thesis: (1) effects of different buffer layers on the characteristics of ZnO epitaxial films. (2) effects of annealing treatment conditions on the characteristics of ZnO epitaxial films. By introducing a 400℃ ZnO buffer layer, the quality of ZnO epilayer grown at 500℃ becomes poorer than that of the ZnO grown directly on the sapphire substrate. However, by introducing a 450℃ ZnO buffer layer, the quality of ZnO epilayer grown at 500℃ becomes better than that of the ZnO epilayer grown directly on sapphire substrate. These results reveal that the ZnO buffer layer has significant effects on the performance of the final ZnO epilayer. On the other hand, the thermal annealing effect on the ZnO epilayer grown on sapphire substrate at 450℃ was investigated using various atmospheres (i.e. air, nitrogen and oxygen). It was found that the ZnO epilayer annealed at 900℃ under N2 atmosphere showed a flat surface and better crystalline quality while a rough surface and poor crystalline quality was obtained under O2 atmosphere. The ZnO epilayer annealed under N2 atmosphere showed poorer electrical property than that annealed under O2 atmosphere. As a result, the variation of oxygen vacancy in the ZnO epilayer after annealing could contribute these points.
Appears in Collections:材料科學與工程學系



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