压电调制超宽禁带氮化物/过渡金属硫化物混合维度异质结电子特性的机制研究

Under the background of demand-driven semiconductor technology, the use of piezoelectric effect to control the electronic properties of semiconductors is an important technical means. Using piezoelectric effect to control 3D/2D mixed-dimensional heterostructure is an advantageous way to achieve the goal. This kind of heterostructure not only has a more flexible and broader application area, but also exhibits novel piezoelectric characteristics that are non-covalently maintained in the out-of-plane direction, and accordingly possess an additional manipulation path of electronic properties. However, the understanding of the piezoelectric mechanism is not deep enough, and the existing dipole model is still rough, while both academics and our previous studies have shown that non-covalent interaction can induce the introduction of novel quantum states, and vertical stress can lead to significant changes of electronic properties. This project proposes the construction of a mixed-dimensional heterostructure of strong piezoelectric AlN and transitional metal dichalcogenides. Firstly, from view of atomic scale, effects of surface reconstruction and interface assembling on the electronic structure are investigated, with revealing the physical mechanism of the novel electronic state. The out-plane strain is then applied to reveal the modulation mechanism of the non-covalent coupling to the electronic structure, and the micro-piezoelectric mechanism model is established. Finally, by constructing the prototype device and experimental characterization, the principle of carrier transport controlled by stress is explored. This project not only systematically explains a novel piezoelectric mechanism, but also lays a theoretical foundation for new piezoelectric devices.

当前以需求为半导体技术牵引的背景下，利用压电效应操控半导体的电子特性是一种重要技术手段，压电调控三维/二维混合维度异质结是其很有优势的实现途径。该类异质结不仅具有更灵活广阔的应用空间，而且在面外方向上显示出非共价作用维系的新奇压电特性，具备额外的电子特性操控途径。但是该压电机制的认识还不够深入，现有的偶极子模型仍较粗糙，而学术界与我们前期研究都表明非共价作用会耦合诱导新奇量子态，此时垂直应力会导致电子特性发生显著改变。本项目提出强压电AlN与过渡金属硫化物构筑混合维度异质结构，首先从原子尺度阐释表面重构和界面组装方式对其电子结构的作用规律，深入研究新奇电子态的物理机理；然后通过施加面外应变，揭示非共价耦合对电子结构的调制机理，建立微观压电机制模型；最后通过构筑原型器件和实验表征，探究应力对载流子输运的操控原理。本项目不仅系统阐释了一种新颖的压电作用机制，而且可以为新型压电器件奠定理论基础。

超宽禁带氮化物半导体和二维层状过渡金属硫化物在面外方向上集成形成的三维/二维混合维度异质结具有灵活的组装形式和能带剪裁形式，在柔性光/电子器件等领域具有很好的应用前景，特别是在异质结面外方向施加垂直应力可以有效调控其特性，为其新颖应用提供了额外途径。本项目基于AlN/MoS2（WSe2）混合维度异质结构开展了面外应变下的电子态特性研究。发现AlN与MoS2（WSe2）均形成I型异质结，因此可以用于基于量子阱等的器件结构，进一步发现异质结界面扭转角以60度为周期，可周期性地调制能带带偏和载流子输运特性。通过施加应力可以有效改变异质结内部层间耦合强度。单层二维材料下，应力显著增强异质结界面处耦合，使AlN表面势垒升高；两层二维材料及以上的情况，应力主要增强二维材料内部层间耦合，使载流子隧穿距离减少。通过构建氮化铝/层状过渡金属硫化物/氮化铝PIN晶体管并计算其伏安特性，发现应力不仅将亚阈值区域内陷阱相关载流子隧穿导电机制转变为PN结正向亚阈值导电特性，而且可以规律性调制器件的输出电流，为垂直应变调控下的新型电子器件应用提供了依据。在完成上述研究之外，项目扩展研究了磁性二维过渡金属硫化物VSe2/三维磁性过渡金属接触界面的自旋输运机制，并提出了一种新型自旋晶体管，相关研究为后摩尔时代新型低功耗器件的设计提供了原理依据和技术参考。