MoS2/WSe2范德瓦尔斯异质结体系隧穿场效应晶体管器件设计及性能研究

As the characteristic dimension of electronic devices approaching to the molecular scale, the contradiction between dimensions and performances of the devices has become more and more prominent, and the research and development of new devices is imminent. Building new devices with van der Waals heterojunctions (vdWHs) constructed by the stacks of two-dimensional materials together has been showing great potential, in particular tunneling field-effect transistor (TFET) devices represented as MoS2/WSe2 vdWHs. However, at present, research work about MoS2/WSe2 vdWHs based TFET devices is still at the stage of exploring. Some problems have limited the improvement of device performance, for instance, the ambiguous band-to-band tunneling mechanism of this heterojunction system and too large contact resistance connecting with the metal electrodes and so on. This project focus on the electronic transport properties of MoS2/WSe2 vdWHs system under the control of gate voltage by using the density functional theory and nonequilibrium Green’s function method. A penetrating research on the contact between the source/drain electrode and the channel material will be done to analyze the influence mechanism of interface and doping effects on contact resistance and device performance. And on this basis we further study the impacts of the stacked layers and scopes of gate insulating layer-hexagonal boron nitride on the device performance. Smooth implementation of this project will provide theory gist for understanding the tunneling mechanism of TFET devices based on two-dimensional materials and exploring a preparation method of high-performance field-effect transistor.

在电子器件特征尺寸接近分子尺度后，器件尺寸与性能之间的矛盾越来越突出，新型器件的研发迫在眉睫。利用二维材料堆叠组成的范德瓦尔斯异质结（vdWHs）体系来构建新型器件，特别是以MoS2/WSe2 vdWHs为代表构建的隧穿场效应晶体管（TFET）器件表现出巨大潜力。然而，目前关于该异质结TFET器件的结构与性能之间的关系仍处于探索阶段，其带-带隧穿机制尚不明确，与金属电极之间接触阻抗过大等问题还十分突出，限制了该器件的性能。本项目将采用密度泛函与非平衡格林函数方法研究该体系在栅极电压调控下的电荷输运性质，深入分析界面效应和掺杂效应对接触电阻和器件性能的作用机理，探索二维栅极绝缘材料-六角氮化硼的堆叠层数以及作用范围对器件性能的影响机制。本项目的开展为人们理解基于二维材料TFET器件的隧穿机制和探究高性能场效应晶体管器件的制备方法提供重要的理论依据。

新型二维半导体材料有望替代传导硅基半导体应用于新一代场效应晶体管器件（FET）中。当前，人们正试图寻找有效的有段来获得高性能的二维半导体FET器件。本项目从金属-半导体接触和材料本身出发，采用密度泛函理论和非平衡格林函数相结合的理论方法，研究了金属与MoS2/WSe2 范德瓦尔斯异质结（vdWH）的接触性能，为金属与异质双层半导体之间的电接触问题提供了新的见解。采用了官能团掺杂电极的方法有效调制了金属-半导体的接触势垒，实现了欧姆接触，表明表面官能团修饰是调控二维电极与半导体材料界面肖特基势垒高度的可行方法。进一步构建MoS2/WSe2 vdWH 隧穿场效应晶体管（TFET）器件，考虑不同电极掺杂浓度下器件的性能，结果表明该器件性能远低于IRDS2020标准，不适宜构建高性能TFET器件。在此基础上，我们改进沟道材料，成功构建亚5 nm单层SiMe -石墨烯n型FET器件，且该器件性能能够满足IRDS2020标准，表明了SiMe -石墨烯有望成为未来FET器件的潜在候选材料。该项目的研究对vdWH型金属-半导体接触的基础研究具有一定的指导意义，而且为高性能vdWH半导体器件的设计提供了指导。