【作者】 高凡；

【导师】 施毅； 刘建林；

【作者基本信息】 南京大学 ， 微电子学与固体电子学， 2015， 博士

【摘要】 半导体纳米线作为典型的一维功能材料,以其特异的性质将在半导体光电子学研究领域占据重要地位。以ZnO材料为例,它具有极大的激子结合能(60 meV)和优异的光电特性,是在室温下实现高效、低阈值紫外激光器的理想材料。对纳米线而言存在一个材料组装的问题,实现大规模定向排列与集成的纳米线阵列是获得可靠器件性能的基础。本论文重点对纳米线材料的组装方法和ZnO纳米线随机激光器进行了研究和探索。我们发展了一个通用的图形化方法,获得了功能衬底并实现了大规模定向排列的纳米线阵列;研究了ZnO纳米线电浦随机激光器,分别实现了基于p-n结结构和肖特基结构的随机激光器件。大规模纳米线阵列的实现有利于纳米线器件的制备,新的器件结构也为微型半导体激光器的发展提供了新方向,对于纳米线器件应用有重要意义。本文取得的创新结果如下：(1)提出一个利用激光干涉实现自组装单分子膜图形化的方法,制备了具有亲疏水性差异的功能衬底,并获得了大规模精确排列的纳米线阵列。该图形化方法具有普适性,可用于大面积界面修饰及功能化的实现。我们制备出亲疏水条纹衬底并用作转移模板,利用流体作用力将溶液中的离散纳米线排列、集成到转移模板的亲水区域,获得了大规模精确组装的纳米线阵列,为纳米线基功能器件发展提供了技术基础。(2)为了提高纳米线器件的电流注入效率,我们提出并制备了一种全新的侧面电极结构。该结构利用阳极氧化的方法在Al电极上制备A1203作为绝缘层结构,形成了上下电极、纳米线和绝缘层间的相互匹配,为纳米线器件提供可靠的电学接触。该侧面功能电极与纳米线具有大的接触面积和短的载流子输运路径,有利于提高纳米线基器件的电学注入/抽取效率。(3)实现了ZnO纳米线p-n结电浦随机激光器。我们通过CVD方法生长氮掺杂ZnO纳米线,和非掺杂的种子层薄膜形成p-n同质结。器件的光电流和Ⅰ-Ⅴ测试结果表现出p-n结结构特性。随后对该器件进行电泵浦激励,在EL光谱上波长390 nm波段观测到随机激光发射峰,输出功率和注入电流的关系也呈现阈值特性,开启电流大约40 mA。研究认为激光的产生是源于强散射形成的闭合回路谐振腔所提供的正反馈,表明ZnO是实现室温激光器的理想材料。(4)提出并制备了Au-ZnO纳米线肖特基结电浦随机激光器,这是首次在肖特基结器件结构中观测到随机激光发射现象。非掺杂的ZnO纳米线具有本征n型导电性,与蒸镀在纳米线顶端的Au薄膜形成Au-ZnO肖特基结。器件在正偏压下EL光谱上探测到随机激光发射峰,同时100 mA注入电流下输出功率约为67 nW,高偏压下还观测到Zn原子表面等离激元相关的发射峰。研究表明激光的产生源于ZnO内的激子激光发射。在足够高的正偏压下空穴从正极隧穿到ZnO价带,与导带上的电子形成激子发光。该研究结果的重要意义是：它表明在肖特基二极管中少量的空穴载流子注入即可激发随机激光,其形成的激子起到主导作用。我们的研究为微型半导体激光器的发展提供了新的器件结构。更多还原

【Abstract】 Semiconductor nanowires are typical 1D materials which will play an important role in semiconductor optoelectronics area for their unique physical properties. For example, ZnO owns large exciton binding energy (60 meV) and remarkable optoelectronic properties, which is perfect candidate for low threshold and high performance UV lasers. Large scale alignment and assembly of nanowires is the fundamental of stable device performance. This work focuses on the large scale assembly of discrete nanowires and ZnO nanowire random lasing. A general micropatterning method for functional substrate is developed and large scale ordered nanowire arrays were achieved. ZnO nanowire random lasers based on p-n homojunction and Schottky junction were also realized in this work. Large scale assembly of nanowire arrays is the fundmental of nanowire based device fabrication, and Schottky junction provides alternative device structure for the development of semiconductor random lasing, which are important for nanowire device application.The main results are obtained as follows:(1) A laser induced SAM patterning method is developed in this work and functional substrate with alternative wettability was fabricated. Large scale precisely aligned nanowire arrays were realized. This technique is general and scalable, exhibiting significant application potential in surface engineering and functionalization. Patterned OTS/SiO2 substrate with alternating wettability was fabricated and used as receiver substrate to assemble discrete nanowires from solution. Large scale precisely aligned nanowire arrays were deposited on the hydrophilic areas by the interaction of microfluidic force and shear force, which provides technical fundmental for nanowire based devices.(2) A method of fabricating lateral electrodes on nanowires is developed to improve the injection efficiency in optoelectronic devices. The method uses Aluminum as bottom electrode material, involving with the nanowire transfer and the anodic oxidation process. Structurally matched alumina insulates the electrodes and provides reliable electrical contact. This lateral electrode propels carriers to transport them across nanowires and is crucially beneficial to the injection/extraction in devices.(3) Electrically pumped ZnO p-n homojunction random lasing is demonstrated. Nitrogen-doped ZnO nanowires were grown on ZnO thin film by chemical vapor deposition. The p-n junction behavior was studied by the photocurrent as well as the I-V characteristics. The device was then electrically pumped. The random lasing behavior was detected around 390 nm in the EL spectra and decent output power of 118 nW at 70 mA was also measured from this device. Lasing was generated from the formation of close-loope cavities by strong scattering and ZnO is a perfect candidate for room temperature nanolasers.(4) First electrically pumped random laser based on Schottky juntion is proposed. Undoped n-type ZnO bundle nanowires were grown on ZnO seed thin film layer. Au metal was deposited on the top ends of the nanowires to form metal-semiconductor junction. Good random lasing behavior was detected in the EL spectra and the output power was about 67 nW at 100 mA. Furthermore, Zn plasma is observed near 320 nm and 480 nm at high current of 100 mA. This research indicates that the leakage hole current flowing in Schottky junction is sufficient to help trigger excitonic process in ZnO nanowires, and initiate and maintain excitonic lasing. This study provides an alternative device structure for the development of semiconductor random lasers.更多还原