基于平行阵列碳纳米管的射频晶体管和电路

Because of its extremely high mobility, saturation velocity and special atomic structure, carbon nanotube (CNT) is regarded as the most promising material for the next generation nanoelectronic devices. However, device based on a sinle CNT has large parastic capacitance and allows only small current, and therefore is not suitable for application in radio frequency (RF) circuits. On the other hand, ordinary CNT film contains metallic CNTs which affect the performance of the CNT film devices. In this project, we propose to fabricate, directly on the as-grown CNT film on insulating quartz substrate, RF devices and circuits. By using the quartz substrate and optimized device structure, parastic capacitance associated with the device can be significantly reduced. In addition, by using dense arrays of parallel CNTs as the channel material, the working current of the CNT device can be significantly increased and contact resistance reduced, yielding in principle devices with a cut-off frequency that is higher than that based on conventional semiconductors. The strong interaction between the CNT and the quartz substrate can also be utilized to break the structural symmetry of the metallic CNTs to transfer them into semicondicting CNTs. The stringent requirement on the controlled growth of CNT thin film is thus relaxed. This project also intend to fully utilize the ambipolar field-effect characteristics of the CNT thin film devices to construct high performance and novel RF circuits, including frequency doubler, mixer and amplifier circuits.

碳纳米管材料由于其超高的载流子迁移率和饱和速度，特殊的原子结构，被视为是构建下一代纳电子器件的理想材料。但是基于单根碳纳米管的器件电流小，寄生电容大，不适于构建射频电路。基于碳纳米管薄膜的器件由于薄膜中包含金属性的碳纳米管，器件性能受到了极大的限制。本项目拟采用直接生长在绝缘石英基底的平行碳纳米管阵列作为器件材料，直接加工器件并进一步构建射频电路。采用绝缘石英基底和合理设计器件结构可以极大地降低器件寄生电容，使用高密度的平行碳纳米管阵列可以大幅度提高器件的开态工作电流，有效地降低接触电阻，实现超越传统半导体的截止工作频率。利用碳纳米管和石英基底的强相互作用，可以破坏碳纳米管结构的对称性，进而将金属型的碳纳米管转换成为半导体型碳管，解决高性能碳纳米管薄膜器件对于材料可控生长的苛刻要求。本项目还拟充分利用碳纳米管器件的双极特性，设计并构建新型高效射频电路，包括倍频器，混频器和放大器。

本项目采用碳纳米管薄膜作为沟道材料构件射频晶体管和电路。项目系统研究了碳纳米管薄膜的制备，碳纳米管纯度对器件和电路的影响，适合碳纳米管器件的高k栅介质；发展了一般碳纳米管功能单元的加工方法，并在这个基础上制备出了整体尺寸小于100纳米的最小二极管，中等规模的集成电路；从理论和实验探索了决定碳纳米管电路速度的关键因素，大幅提高了碳纳米管电路的速度； 在石英基底上通过化学气相方法制备了高密度定向排列碳纳米管平行阵列，利用石英晶格与碳纳米管的强相互作用，制备出了高性能双极晶体管，基于这种新器件原理，设计并制备出了高性能的射频集成电路, 包括倍频器、混频器, 其工作频率高达40 GHz, 为碳基电路中最高水平。项目发表论文30篇，其中影响因子大于10的研究论文9篇，影响因子大于7的研究论文12篇。相关结果被自然杂志和英国物理学会网站作为研究亮点专文介绍，被2015年的《中国-自然指数》重点介绍，称其“代表了计算机处理器的未来”。