Study of ZnO based heterostructures towards realizing high-luminous efficiency ultraviolet to blue light-emitting diodes

自2005年第一个同质外延发光二极管（LED）问世以来，氧化锌（ZnO）因其优异的上级性能而受到越来越多的关注。其性能的影响预计将从高发光效率跨越到低成本和清洁生产力，利用丰富的来源和商业上可用的单晶衬底。本研究的目的是提高电致发光（EL）效率的导电ZnO衬底上制作的LED，其中垂直接触的几何形状可以利用更可取的实际应用。利用分子束外延技术，我们制备了由p型和n型MgZnO势垒层夹在ZnO阱层之间的双异质结构。结果，实现了高效的带边缘EL。因此，我们的研究为商业产品的开发铺平了道路。寻找一种透明的金属材料来形成金属薄膜也是一个重要的研究课题 ...更多信息 与p型层有良好的欧姆接触。我们发现，具有大的功函数的导电聚合物具有良好的性能以及适用于使用简单的旋涂。此外，这种聚合物被发现是非常有用的肖特基接触的n型ZnO。然而，一些技术问题，如适当的空穴浓度的分析和氮的掺杂效率的提高仍有待解决的未来。在与本研究相关的其他观点中，可以获得一些显着的成果：（1）在MgZnO/ZnO异质结构中观察到量子霍尔效应（发表在Science，高影响力期刊之一）（2）具有创纪录长的光致发光寿命的MgZnO薄膜的外延生长，这两个都表明了最先进的技术。总体而言，所取得的成绩是显著的，对建议书的内容是满意的。此外，通过本研究，为下一步的研究课题（氧化物半导体低维结构中的输运性质研究）获得了基本的思想、知识和技术。少

Zinc oxide (ZnO) has been attracting increasing attentions due to their superior properties for making ultraviolet to blue light-emitting diodes (LED) since the first homoepitaxial LED was realized in 2005. Impacts of their performance are expected to span from high-luminous efficiency to low-cost and clean productivity, taking advantages of abundant source and commercially available single-crystalline substrates. This study aims at improvement of electro-luminescence (EL) efficiency of LED fabricated on conducing ZnO substrates, where vertical contact geometry can be utilized being preferable to practical application. Using molecular beam epitaxy technique, we have fabricated double-heterostructures consisting of ZnO well layers sandwiched by p-and n-type MgZnO barrier layers. As a result, highly efficient band-edge EL is realized. Thus, our study paves a way for development of commercial products. It is also an important protocol to search a transparent and metallic material to form … More good Ohmic contact to p-type layer. We find that a conducting polymer having a large work function has good properties as well as applicability for the use of simple spin-coating. Moreover, this polymer is found to be very useful for making Schottky contact to n-type ZnO. Nevertheless, a few technical issues such as proper analysis of hole concentration and improvement of doping efficiency of nitrogen remain to be solved in future. In other viewpoints associated with the present study, some notable achievements can be obtained; (1) observation of quantum Hall effect in MgZnO/ZnO heterostructures (published in Science, one of high-impact journals) (2) epitaxial growth of MgZnO films having record-long photoluminescence lifetime, both of which indicate state of art technology. Over all achievements can be considered remarkable and satisfactory to contents of proposal. Furthermore, basic idea, knowledge and techniques for pursuing next research subject (study of transport properties in oxide semiconductor low-dimensional structures) have been acquired through this study. Less