臺灣博碩士論文加值系統

本篇論文是以氣相冷凝方式在基板上覆蓋多孔鋁模板於低溫下成長氧化鋅奈米結構與光學特性量測，並嘗試應用於p-n接面，以ZnO摻雜In降低電阻率，研究p-GaN與n型ZnO:In 接面發光特性。
首先，以氣相冷凝方式將置於鎢舟之氧化鋅粉末受熱昇華成氣體分子而向基板移動，在抽氣氣流協助下，使得氧化鋅氣體分子更易穿過多孔陽極氧化鋁模板，氧化鋅的氣體分子在多孔陽極氧化鋁模板內緩慢的成核與成長，逐漸地產生微小的奈米晶核(nucleus)沉積在基板上，由於基板溫度一直保持在液態氮的溫度(-196℃)，基板的低溫會阻止奈米晶核的繼續橫向成長進而得到氧化鋅奈米粒子，隨著奈米粒子在孔徑內的累積，最後移除多孔陽極氧化鋁模板得到氧化鋅奈米結構。以電子顯微鏡(FE-SEM)觀測氧化鋅奈米結構呈六角柱狀，直徑約50nm，長度約略50~70nm，發現Sapphire上的氧化鋅奈米線具C軸優先取向特性，外觀呈現較有序、相互平行型態，容易達成光子晶體所要求的規則性排列。氧化鋅奈米線經光激發光譜發現紫外光波段要比綠光波段強度強，顯示以低溫成長的氧化鋅奈米結構光學性質優於高溫製程下得到的產物。
接著，將本研究所備製之氧化鋅結構沉積在P型氮化鎵表面以製作P型氮化鎵與N型氧化鋅結構之p-n 發光二極體元件，探討此元件之發光原理。此外，為提升N型氧化鋅之載子濃度，於氧化鋅製作過程中參雜銦原子，經過電致發光量測在p-GaN/n-ZnO:In 接面有藍光產生，為了完成氧化鋅發光元件之製作，加入未參雜氧化鋅結構，完成p-i-n發光二極體異質接面結構，經電致發光量測結果顯示，發光波段為氧化鋅能隙之紫外光波段。

In this study, the materials characteristic and optical properties of ZnO nanostructures which fabricated by vapor cooling condensation system with anodic alumina membranes at low temperature were investigated. Due to their lower resistivity, In element was introduced into these ZnO nanostructures and apply to a p-n junction of p-GaN/n-ZnO:In structure. By this method, the associated electroluminescence properties of this p-GaN/n-ZnO:In structure were discussed.
Initially, ZnO powders heated on tungsten boats by vapor condensation way sublimate the related gas to the cooled substrates. Under the pumping air assistance, it helps vaporized ZnO member to be easier to pass through the anode aluminum membrane (AAM). Using ZnO gas member slowly coring and growth in the AAM gradually, small nucleus was deposited on the substrate. Along with ZnO nanoparticles in aperture accumulation, ZnO nanowires can be obtained after removing the AAM.
Using the FE-SEM observation of ZnO nanostructures, it can be seen that the grown ZnO nanostructures are hexagonal close-packed Wurzite structure, with diameter approximately 50 nm and length about 50 ~ 70 nm. Compared with the different substrates, ZnO nanowires grown on the sapphire have the C axis preferred orientation characteristic. In addition the outward appearance presents comparatively has the foreword, mutually parallel condition which is easy regularity arrangement to achieve the request of photonic crystals.
According to the photoluminescence spectra of the ZnO nanostructures measured at room temperature, a stronger UV emission (380nm) and weaker green emission (500nm) is observed. It demonstrated growing ZnO nanowires at lower temperature optical quality is better than the product grown at a higher temperature processing regulation obtains.
Despite of the difficulty of p-type doping ZnO has impeded the fabrication of ZnO p-n homojunction devices. An exchangeable approach to homojunction, n-ZnO/p-GaN heterohunction has been suggested as a stronger candidate for device applications. Doping In element into ZnO structures could lower resistivity and increase conductivity. With EL measurement the junction of P-GaN/ZnO:In could see blue light.
In addition, ZnO structures prepared in this study deposited on p-GaN surface to fabricate p type GaN and n type ZnO heterostructure and research the shine principle. Besides, doping Indium atoms to improve the carrier concentration of n-type ZnO structures. With EL measurement the junction of p-GaN/n-ZnO:In could see the blue light. In order to accomplish the fabrication of ZnO light emitting device, in this study undoped ZnO film is inserted between p-GaN and n-ZnO:In films to form p-i-n heterojunction. As a result, an ultraviolet emission at the peak of 385 nm, related to ZnO exciton recombination, was observed in a room-temperature electroluminescence spectrum of p-i-n heterojunction under forward bias.

Abstract (Chinese) / I
Abstract (English) / II
Acknowledgements /IV
Contents / V
List of Tables/ VII
List of Figures / VIII

Chapter 1 Introduction / 1
Chapter 2 Fabrication and Measurement / 4
2-1 Vapor cooling condensation fabrication method / 4
2-2 Analyses system / 6
2-2.1 Scanning electron microscopy (SEM) /6
2-2.2 Photoluminescence (PL) /7
2-2.3 Hall measurement /9
2-2.4 Electroluminescence /9
Chapter 3 Results and Discussion /10
3-1 Scanning Electron Microscopy (SEM) Results /10
3-2 Photoluminescence (PL) Results /12

Chapter 4 Investigation of p-GaN/ZnO:In heterojunction /15
4-1 The procedure of p-n junction /17
4-1.1 Doping procedure /17
4-1.2 Annealing procedure /17
4-1.3 p-n junction fabrication process /18
4-2 In-doped ZnO results and discussion /20
4-3 P-n heterojunction discussion /23
Chapter 5 Conclusion /25
Reference / 27

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