基于范德华外延生长高质量大面积硫化钼射频晶体管的性能研究

Two-dimensional (2D) semiconductors molybdenum disulfide have received great research attention for applications in the emerging field of ubiquitous electronics in recent years. Because of their atomically thin body nature and tunable bandgap, molybdenum disulfide becomes a promising semiconductor candidate for solving the problem of short channel effect in nanoscale metal-oxide-semiconductor field-effect transistors, and exploring its application in radio frequency devices. Develop the advantages of molybdenum disulfide in radio frequency is an attractive research area. MoS2 is a two-dimensional structure, which is much sensitive to the substrate and gate dielectrics. This poses a great channeling to achieve high-performance molybdenum disulfide radio frequency devices. The first step is to obtain high-quality molybdenum disulfide materials. In this project, we will grow monolayer molybdenum disulfide on molten glass by Van der Waals epitaxial growth system. We will systematically study the growth mechanism and explore the growth parameters to the nucleation. Eventually, monolayer molybdenum disulfide based radio frequency devices will be fabricated after optimizing the device structure and process flow using self-align gate deposition process and buried-gate to reduce parasitic parameters. These developed processes play a prominent part in increasing the cut-off frequency and maximum oscillation frequency of molybdenum disulfide radio frequency devices. Finally, we will investigate molybdenum disulfide radio frequency devices based on flexible substrates. This project not only provides the feasible growth of high-quality molybdenum disulfide by Van der Waals epitaxial growth on molten glass, but also demonstrates the potential of molybdenum disulfide for high frequency applications and flexible wireless communication.

二维半导体材料硫化钼因具有优良的电学特性，在半导体行业中受到广泛关注，特别因其具有超薄的结构和可调控的能带结构，为解决短沟道效应提供了可能，并且在电子器件领域具有应用前景。近年来，使用硫化钼作为沟道材枓制备射频晶体管是发挥硫化钼材枓优势的一个重要研宄方向。由于硫化钼是二维结构，受衬底、栅介质的影响很大，因而高性能的硫化钼射频器件的研制也成为一个极具挑战性的课题。制造高性能的射频器件，首先要制备出高质量的硫化钼材枓。我们在前期研究基础上，将在熔融玻璃衬底上利用范德华外延技术获得大面积、高质量的硫化钼薄膜，深入研究其生长机制和成核条件。同时优化器件结构以及工艺流程，使用自对准、埋栅结构、以及短沟道等方法提升晶体管射频性能，并探索其在柔性领域的应用前景。

二维半导体硫化钼具有原子层厚度以及高迁移率，在低功耗逻辑电路中具有巨大潜力，被认为是后摩尔时代的新型半导体材料。本项目研究了少层硫化钼的外延生长及其高速电子器件。与单层硫化钼相比，少层硫化钼具有的合适的禁带宽度和更高的态密度，因此具有更高的迁移率和更低的接触电阻。通过增加前躯体的质量可以提高其反应浓度来控制三层硫化钼的单晶大小，其尺寸最大可以超过148微米。制备的沟长为5微米的器件开关比达到1012，载流子迁移率为62 cm2V−1s−1，明显高于单层硫化钼（迁移率为33.6 cm2V−1s−1）。对于沟长为40 nm的晶体管，其室温驱动电流达到589 μA/μm，4.3 K时进一步提高到1162 μA/μm，并且低温下没有表现出肖特基现象。器件接触电阻最小达到350 Ω·µm。我们制备并研究了柔性双层二硫化钼射频晶体管。二硫化钼柔性器件的截止频率和最大振荡频率分别为 4 和 9.6 GHz。研究了不同栅极长度器件的射频性能，器件的截止频率和最大振荡频率随着沟道尺寸的减小明显提升。研究了不同弯折条件对柔性器件直流和射频性能的影响。结果显示，不论是改变实验过程中的弯折次数或者降低弯折半径，器件的直流和射频性能均没有明显的下降。本项目的成果对于二维半导体材料在后摩尔时代和物联网领域的应用具有借鉴意义。