Pande Gaurav, Siao Jyun-Yan, Chen Wei-Liang, Lee Chien-Ju, Sankar Raman, Chang Yu-Ming, Chen Chii-Dong, Chang Wen-Hao, Chou Fang-Cheng, Lin Minn-Tsong
Department of Physics, National Taiwan University, Taipei 10617, Taiwan.
Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan.
ACS Appl Mater Interfaces. 2020 Apr 22;12(16):18667-18673. doi: 10.1021/acsami.0c01025. Epub 2020 Apr 13.
To explore the potential of field-effect transistors (FETs) based on monolayers (MLs) of the two-dimensional semiconducting channel (SC) for spintronics, the two most important issues are to ensure the formation of variable low-resistive tunnel ferromagnetic contacts (FCs) and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts, and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated ML WSe FETs using bilayer hexagonal boron nitride (h-BN) as a tunnel barrier at the FC/SC interface. We investigate the electrical transport in ML WSe FETs with the current-in-plane geometry that yields hole mobilities of ∼38.3 cm V s at 240 K and on/off ratios of the order of 10, limited by the contact regions. We have achieved an ultralow effective Schottky barrier (∼5.34 meV) with an encapsulated tunneling device as opposed to a nonencapsulated device in which the barrier heights are considerably higher. These observations provide an insight into the electrical behavior of the FC/h-BN/SC/h-BN heterostructures, and such control over the barrier heights opens up the possibilities for WSe-based spintronic devices.
为了探索基于二维半导体沟道（SC）单层（ML）的场效应晶体管（FET）在自旋电子学中的潜力，两个最重要的问题是确保形成可变的低电阻隧道铁磁接触（FC）以及在制造过程中保持SC的固有特性。大的肖特基势垒会导致形成高电阻接触，而用于控制势垒的方法通常会改变SC的固有特性。这项工作旨在解决完全封装的ML WSe FET中的这两个问题，该FET在FC/SC界面处使用双层六方氮化硼（h-BN）作为隧道势垒。我们研究了具有面内电流几何结构的ML WSe FET中的电输运，该结构在240 K时产生约38.3 cm² V⁻¹ s⁻¹的空穴迁移率，开/关比约为10，受接触区域限制。与势垒高度高得多的非封装器件相比，我们通过封装隧道器件实现了超低有效肖特基势垒（约5.34 meV）。这些观察结果为FC/h-BN/SC/h-BN异质结构的电学行为提供了见解，并且对势垒高度的这种控制为基于WSe的自旋电子器件开辟了可能性。
