基于铁电基底调制的横向二维层状半导体p-n结

Because of their ultimate thickness, layered structure and high flexibility as well, p-n junctions (PNJs) based on layered two-dimensional (2D) semiconductors have been attracting increasing attentions, recently. Based on the device configurations, PNJs can be categorized into vertical and lateral PNJs (VPNJs and LPNJs). The formers are the stacks of different ultrathin 2D layered materials held together by relative weak van der Waals (vdWs) forces and the latters are formed by the seamless ultrathin 2D layered “p” parts and “n” counterparts interconnected by strong in-plane covalent bonding. Since VPNJ is assembled together by weak vdWs forces, there is a vdWs gap between its “p” and “n”. This structure feature may bring up some problems on carrier transport. Comparison with VPNJs, there is more tight connection between its “p” and “n” in LPNJs where are the chemical bonds. .Among various methods to fabricate LPNJs, electrostatically tuning LPNJ by two separated local gates is an efficient approach, with the advantages of ease of fabrication, free of contamination and homojunctions as well. However, to keep the p-n behaviors of 2D layered materials, the external electrical fields applied to the two local back gates have to be continuously maintained. It brings up complex device fabrication processes and high energy cost, which seriously limit the practical applications for electronics and optoelectronics. Here, we take advantages of the unique properties of ferroelectrical materials to supply the required electrical field to support the lateral p-n junctions. Furthermore, through the systematical investigations on the electronic and optoelectronic of this kind of LPNJs, we will try to find the inherent physics how the ferroelectrical characteristics affect the device performance and to propose new p-n junction theory. We believe we will make a series of innovative achievements and this study will play a significant role in promoting the practical applications of TMDCs.

二维层状半导体p-n结在电子、光电子器件领域具有广阔的应用前景。相对于纵向范德华堆垛的p-n结，横向p-n结以较强的共价键连接，有望获得更高的器件性能。在众多横向p-n结构建方法中，静电场调制的方法具有加工简单、无杂质污染、同质p-n结等优点，成为高效的p-n结制备方法。然而，为维持p-n结特性，需提供持续不断的外部电场，因此带来器件结构复杂，高能耗能缺点，严重限制了其实际应用。本项研究针对上述问题，将铁电材料与二维层状半导体结合，利用铁电材料的电滞回线特性，由铁电体的剩余极化强度提供电场对超薄二维层状半导体静电掺杂实现横向p-n结的制备。进一步系统地研究p-n结的电子、光电子性能，探索铁电体性能参数对p-n结性能的调制规律，揭示铁电材料调制横向p-n结的内在物理本质，为推进二维层状半导体p-n结在电子和光电子器件领域的应用打下坚实的实验和理论基础。

二维半导体材料及异质结在电子、光电子器件领域具有广阔的应用前景。本项目围绕铁电极化材料与二维电子材料展开系统研究，取得主要成果如下：.（1）利用铁电材料P（VDF-TrFE）的极化特性，将二维WSe2、MoTe2的导电特性从双极性导电特性调控为单极p型导电；采用铁电材料CuInP2S6与h-BN为共同介电层，通过设计独特的耦合栅极器件结构，在保持开关比达到107的条件下，获得了超大的铁电存储器的存储窗口达到104 V；基于铁电材料CuInP2S6的负电容特性，实现了超陡峭亚阈值摆幅的全二维晶体管器件，亚阈值摆幅最小达到了6.1 mV/Dec，远远低于玻尔兹曼热力学极限60 mV/Dec。.（2）范德华异质结具有出色的光电性能，但是由于层间范德华间隙引入的隧穿势垒限制了光电器件性能。针对这一弊端，项目组发展了横向异质结构和桥接异质结构。这种无间隙的异质结构筑的光电晶体管在光触发开关比和光响应时间有着显着改善，例如：响应速度提升超过5个数量级，响应速度提升超过4个数量级。.（3）利用二维电子材料具有超薄厚度、表面光滑无悬挂键、可人为任意堆垛等重要特点，项目组构筑了基于石墨烯、氮化硼、二硫化钼和二碲化钼的非对称范德华异质结器件。在不同的偏压条件下，电荷载流子注入类型可以在隧穿和热激活之间切换。该研究实现了超高器件性能与多种功能集成的有机统一。.经过4年的研究发表相关研究成果34篇，其中影响因子大于10的论文25篇，包括Nature Electronics 1篇，Nature Communications 1篇，Chemical Society Reviews 1篇，Advanced Materials 8篇，Nano Letters 3篇，ACS Nano 2篇， Advanced Functional Materials 5篇， Advanced Sciences 1篇，Nano Energy 1篇等。受邀撰写综述论文4篇。申请中国专利7项，其中已授权3项。