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標題: | 利用脈衝雷射沈積系統製作氮化鎵磊晶層在氧化鋅緩衝層上及光電特性量測 Fabricating Gallium Nitride Epilayer on Zinc Oxide Buffer Layer via Pulsed Laser Deposition System and Opto-electric Properties Analysis |
作者: | Chun-Wei Ku 古竣偉 |
指導教授: | 林清富(Ching-Fuh Lin) |
關鍵字: | 水熱法,氧化鋅薄膜,脈衝雷射沈積系統,氮化鎵,氮氣操作氣壓, hydrothermal method,zinc oxide (ZnO),pulsed laser deposition (PLD),gallium nitride (GaN),nitrogen operating pressure, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 本論文主要研究為利用水熱法製作高品質氧化鋅中介層及利用新式PLD在氧化鋅中介層上製作高品質之氮化鎵薄膜。在論文之中,我們首先介紹如何利用水熱法來製備出氧化鋅薄膜。接著我們將此氧化鋅中介層作為磊晶基板,利用新式PLD並調整不同氮氣操作氣壓對於氮化鎵薄膜特性的影響。
在製作高品質氧化鋅中介層部分,我們已經成功的利用水熱法調整不同生長溶液濃度及生長時間製造氧化鋅微奈米柱在氮化鎵磊晶層上,並利用化學動力學探討其在不同生長溶液濃度下氧化鋅微奈米柱體積與生長時間之關係: ,並成功找到合適的生長溶液濃度及生長時間可以製作出氧化鋅薄膜在氮化鎵磊晶層上。緊接著,我們利用AFM量測此薄膜之表面粗糙度,發現其表面粗糙度約在5.46 nm;然後利用EDS量測此薄膜組成之元素比例,發現到此薄膜為高純度之氧化鋅,無其他雜質摻雜在其中;除此之外,我們也利用XRD量測此氧化鋅薄膜的結晶性,結果發現此氧化鋅薄膜具有強烈的c軸取向且在氧化鋅(0001)晶格面之半高寬值為 ,此實驗結果可與利用PLD磊晶出的氧化鋅薄膜之結果不相上下,表示利用簡易且低溫的水熱法也可以製作出結晶品質相當好之氧化鋅薄膜,因此可以將此高品質氧化鋅薄膜應用在許多領域上;最後,我們更進一步地製作氧化鋅薄膜及p型氮化鎵磊晶層的發光元件,結果成功的得到具整流性的電流電壓曲線,在順向偏壓下,也發出了肉眼可見的可見光。 緊接著,我們將此高品質氧化鋅中介層作為磊晶基板,利用新式PLD沈積氮化鎵薄膜在其上。由於在沈積過程中,高能離子束會與環境中的氮氣發生碰撞或散射,此現象會大大影響氮化鎵薄膜之結晶性。然而我們找到當基板加熱溫度為900 oC、600 mJ/pluse的雷射能量、7 Hz的雷射重複頻率及氮氣操作氣壓在1x10-2 torr時,此氮化鎵薄膜在可見光範圍之平均透光度為87 %,且此條件下的氮化鎵薄膜元素比例也最為接近一比一,然而在此條件下所製作之薄膜不僅為c軸取向之單晶氮化鎵薄膜,且在(0002)面之半高寬值為2θ=0.293o,此數值與外界購買之氮化鎵基板((0002)面之半高寬值為2θ=0.301o)不相上下,除此之外,在此條件下的氮化鎵薄膜表面粗糙度為1.6312 nm,即表示此高品質氮化鎵薄膜相當平整。 The study of this thesis is to investigate the hydrothermal method for growing high-quality zinc oxide thin film and the homemade pulsed laser deposition system for fabricating high-quality gallium nitride thin film on zinc oxide buffer layer. First, we introduce to obtain high-quality ZnO thin film via hydrothermal method. After that, we use homemade PLD to fabricate high-quality GaN thin film on ZnO buffer layer, and then the effect of nitrogen pressure on properties of GaN thin film is also investigated. In the study of growing high-quality ZnO thin film, the ZnO thin film was successfully fabricated on the p-type GaN epilayer via the hydrothermal method. We successfully used chemical kinetics to simulate the relationship of the growth concentration and the growth time, thus determining the optimal conditions to fabricate the ZnO thin film on a p-type GaN epilayer. Subsequently, we used AFM, EDS, XRD, and Hall measurements to analyze the characteristics of the ZnO thin film. The roughness of the ZnO thin film is determined by AFM to be about 5.46 nm, where there is no other impurity detected in the EDS spectrum. Besides, under the growth temperature of 90°C and the growth concentration of 100mM for 6 hours, the XRD FWHM of ZnO (0001) shows =0.1682°, which is neck and neck with that fabricated by PLD. This means that it is possible to fabricate good quality ZnO thin film via a low cost hydrothermal method and it can be applied in many fields. We have further fabricated n-ZnO layer onto p-GaN layer to fabricate hetero-junction LEDs and successfully achieved a rectifying I-V curve and light emission from current injection. The EL emission of the LED is dominated in the ZnO layer. All results show that the ZnO thin film fabricated by the low-cost hydrothermal method has good potential for possible applications in the industry of light-emitting diodes and take the place of GaN for the material of emitting layer. Next, we use homemade pulsed laser deposition system to epitaxy high-quality gallium nitride thin film on zinc oxide buffer layer. During the deposition process, the high energy plume collides or scatters with nitrogen in atmosphere. This phenomenon greatly affected the crystalline of GaN thin film. The experimental data shows that the properties of GaN thin film fabricate under deposition condition substrate heating temperature 900 oC, laser energy 600mJ/pulsed, 7 Hz laser repetition frequency, and operating nitrogen pressure at 1x10-2 torr are very good. The UV-visible spectrum shows that average transmittance in the visible range is 87 % , and the EDS spectrum reveals that the element ratio of Ga and N is approach to 1:1. The XRD FWHM of the GaN (0002) thin film shows =0.293°, which is neck and neck with that deposited by MOCVD. Furthermore, the surface roughness of the GaN thin film is only 1.6312 nm. It means that this high-quality GaN thin film is also fairly flat. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62853 |
全文授權: | 有償授權 |
顯示於系所單位: | 光電工程學研究所 |
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