有序Si纳米线Ge/Si量子点复合结构的溅射制备及其性能研究

With technical progress, traditional devices can't satisfy the requirement for faster and smaller devices. Therefore, the research of nanowire devices is one of hot topic in semiconductor field. Because Quantum dots (QDs) are desirable materials as intrinsic layer in p-i-n junction nanowire devices, the integration of QDs and nanowires (NWs) has attracted huge interest. In this project, Ge/Si QDs are prepared on the surface of NWs or on the top of NWs by ion beam sputtering deposition which is one technique easy to implement industrial production. The growth mechanism and photoelectric properties of these composite structures, Ge/Si QDs on/in Si NWs, will be studied systematically. Based on nanosphere template and metal assisted chemical etching, two original methods are proposed for ordered Si NWs fabrication. And the effect of technological parameter of these methods on nanowire structure will be investigated. After change the incidence angle of sputtered atoms injected into Si NWs, the Ge atoms could be controlled to absorb on the surface of Si NWs or on the top of Si NWs, then the Ge/Si axial QDs in Si NWs and Ge/Si coaxial QDs on Si NWs can be formed under the appropriate conditions. The evolution of Ge/Si QDs on/in Si NWs will be discussed under the different growth conditions. The strain in Ge/Si QDs and Si NWs will also be studied. The relationship between Ge/Si QDs growth mode on/in Si NWs and Si NWs size also need be confirmed. According to the structure of Ge/Si axial QDs in Si NWs, a novel composite structure with Ge/Si QDs integrated Si NWs is designed, where the coxial QDs surround the axial QDs. Furthermore, the influence of band gap modulation, optical resonance coupling, resonant tunneling, and decoupling characteristic on the photoelectric properties of these composite structures should be analyzed. A favorable QDs/NWs composite structure will be obtained after this project accomplished. These researches will establish a good foundation to realize optoelectronic integrate using silicon-based materials and to fabricate new nano-photoelectric devices.

传统器件已不满足更快更小的要求，因此纳米线器件成为研究的热点。量子点作为p-i-n型纳米线器件的理想i层材料，将它与纳米线集成激起了人们极大的兴趣。本项目采用可产业化的溅射沉积技术实现Ge/Si量子点和Si纳米线的集成，研究Si纳米线Ge/Si量子点复合结构溅射生长的物理机制及其光电性能。从制备有序Si纳米线新方法的提出入手，探索不同工艺参数对纳米线结构的影响；控制溅射原子入射Si纳米线的角度，寻找合适的沉积参数，实现纳米线轴向和共轴量子点复合结构，研究纳米线上量子点的演变规律，探讨纳米线和量子点中的应变状态，揭示量子点生长模式与纳米线尺寸的关系。基于纳米线轴向量子点，设计并试制一种新型的纳米线量子点复合结构。分析带隙调制、光学共振耦合、共振隧穿及解耦特性等因素对纳米线量子点复合结构光电性能的作用，获得性能良好的纳米线量子点复合材料，为实现Si材料光电子集成和新型纳米光电子器件研制奠定基础。

利用有序阵列构成的光腔来增强量子点的发光，是新型纳米光电材料的研究热点，因此本项目研究了有序Si纳米线Ge量子点复合结构能的制备和发光特性。主要研究内容是：探究了制备有序Si纳米线阵列的新方法；研究了离子束刻蚀过程中轰击时间、束流和电压对聚苯乙烯纳米球直径、有序性和形状的影响，探讨了离子束刻蚀聚苯乙烯纳米球的物理机制；研究了离子枪的极板间距对Si缓冲层质量和Ge量子点生长的影响，讨论了混晶和晶化缓冲层上生长Ge量子点的物理机制，研究了停顿时间对Ge量子点二次生长及尺寸优化的作用；以高密度单层Ge量子点为有源层，研制了金属-Ge量子点-金属结构的光电探测器，初步表征了器件的光电特性；研究了Si纳米线上薄膜生长的厚度均匀性随偏转角度的演变规律，分析了包覆薄膜以后纳米线的形貌变化机制，从Si纳米线上Ge薄膜的形貌变化探讨了纳米线上Ge量子点生长的物理机制，对比分析了有序Si纳米线Ge量子点复合结构增强发光的效果，研究了该复合结构的光致发光特性随激光功率和测试温度的演变规律和物理机制。. 重要结果和关键数据：实现了离子束刻蚀结合金属辅助化学刻蚀制备有序Si纳米线阵列的新方法；离子束技术的刻蚀速率较慢，适合刻蚀直径小于200 nm的纳米球阵列；离子枪极板间距为2 mm时能获得晶化的薄膜和高密度Ge量子点；停顿时间为60 s时，量子点的尺寸均匀性最优；以单层量子点为有源层的光电探测器的内量子效率最大为35.52 %；当偏转角度为15o时，能在Si纳米线外包覆厚度均匀的薄膜；实现了Ge量子点同时在Si纳米线侧壁和顶端的溅射生长，Ge量子点直径为25-40 nm；有序Si纳米线Ge量子点复合结构的发光峰强度比平衬底上自组织Ge量子点的发光峰高一个数量级；发光峰的强度都随着激光功率的增加而增大，1770 nm峰的发光强度的增幅较大；随着测试温度的升高，发光峰出现了红移现象，当测试温度高于77 K时，峰位位于1650 nm的发光峰消失。这些研究为新型高效发光二极管和光电探测器的发展和应用奠定了坚实的基础。