在SiC衬底上原位生长石墨烯的PN结及其特性研究

In recent years, graphene p-n junction exhibits novel physical phenomena and potential application, which makes it become a hot topic of research on graphene. However, the existing preparation methods for graphene p-n junction have more or less some limitations. So, improving the existing method and exploring new technology is a base to realize application of graphene p-n junction. However, exploring a controllable in situ preparation of graphene p-n junction on an insulating substrate with adjustable doping concentration in a p-n junction is a prefer step towards application of graphene bipolar device. Here we explore pioneered method of in situ fabrication of graphene p-n junction on a SiC substrate. Through adjusting doping concentration of a patterned SiC substrate by ion implantation, together with an epitaxial growth of graphene on it by thermal decomposition of SiC, it is expected to control carrier polarity and concentration in graphene and to fabricate graphene p-n junction or periodic structure with expected carrier concentration. The study on transport properties and assessment on detection performance on light from a graphene p-n junction will reveal the key parameters affecting characteristics of graphene p-n junction, which will be helpful to improving the technology for graphene p-n junction. In addition, the technology developed here is compatible with modern semiconductor device procedure and is expected to be an in situ preparation method for graphene p-n junction in large scale, which is significat for realizing application of graphene p-n junction and exploring new functional devices of graphene.

石墨烯PN结展现出新奇的物理现象和诱人的应用前景，使其成为当前研究的热点。然而，现有石墨烯PN结的制备方法或多或少有一定的局限性。完善现有石墨烯PN结制备技术和探索新的制备方法是实现石墨烯PN结应用的基础和方向。而探索在绝缘衬底上原位、可控制备石墨烯的PN结和有效调控PN结的掺杂浓度是实现石墨烯双极器件应用的首选方向。本课题首创了一种原位在SiC衬底上生长石墨烯PN结的方法。通过离子注入对SiC衬底进行图形化的掺杂调控，并采用高温热分解方法原位外延生长石墨烯, 从而实现SiC上石墨烯载流子极性和浓度在空间上的调控，并制备出石墨烯PN结或周期结构。通过对石墨烯PN结输运性能和光探测性能的评估，揭示影响石墨烯PN结性能的关键参数，为提高石墨烯PN结制备水平提供理论指导。该技术与现代半导体器件工艺技术兼容，有望发展出原位、规模化制备石墨烯PN结的新技术，为石墨烯新型功能器件的探索和应用奠定基础。

石墨烯PN结展现出新奇的物理现象和诱人的应用前景。然而，现有石墨烯PN结的制备方法或多或少有一定的局限性。完善现有石墨烯PN结制备技术和探索新的制备方法是实现石墨烯PN结应用的基础和方向。而探索在绝缘Si极化的SiC衬底上原位、可控制备P型石墨烯是制备石墨烯PN结的基础。本课题首创了一种原位在Si极性的SiC衬底上生长P性石墨烯的方法。通过离子注入对SiC衬底进行图形化的掺杂调控，并采用高温热分解方法原位生长石墨烯, 从而实现SiC上石墨烯载流子极性和浓度的调控。通过借鉴SiC晶体P型掺杂方法和常用掺杂元素，以及参考各种掺杂元素在石墨烯生长条件下的饱和蒸汽压，筛选出采用硼离子对SiC进行注入，并生长P型石墨烯的优化技术方案。系统研究了对SiC进行不同硼离子注入深度和注入浓度下所生长石墨烯的形貌、载流子类型和输运特征。发现了稳定生长高质量P型石墨烯的B离子注入深度和浓度。 该方法制备的石墨烯在室温下的载流子浓度为1-5E12cm-2,对应的载流子迁移率为100-300 cm2/Vs，与无注入的SiC上生长的N型石墨烯的输运性能相当。表明通过B离子注入改变石墨烯的载流子类型是可行和可靠的方案。同时，实验中我们意外发现，在非极性的SiC衬底上原位生长的梭形石墨烯条带沿条带长度方向载流子分布呈现类NPN的三极管分布结构。该结构为研究纳米尺度的石墨烯三极结的性能提供了可能。另外，基于SiC上石墨烯形成的垂直肖特基器件显示出具有类似PN结的优异输运性能，使其在0-5V的偏压范围内实现石墨烯/SiC紫外探测器响应速度7个数量级的调控。这些研究成果一部分已公开发表在重要的国际学术期刊上。目前已发表标识课题资助号的研究论文15篇，授权发明专利6项。