Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
Materials Science and Engineering Graduate Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States.
ACS Appl Mater Interfaces. 2023 Apr 12;15(14):18012-18021. doi: 10.1021/acsami.2c22014. Epub 2023 Mar 28.
The ultrathin nature of two-dimensional (2D) materials opens up opportunities for creating devices that are substantially thinner than using traditional bulk materials. In this article, monolayer 2D materials grown by the chemical vapor deposition method are used to fabricate ultrathin all-2D lateral diodes. We show that placing graphene electrodes below and above the WS monolayer, instead of the same side, results in a lateral device with two different Schottky barrier heights. Due to the natural dielectric environment, the bottom graphene layer is wedged between the WS and the SiO substrate, which has a different doping level than the top graphene layer that is in contact with WS and air. The lateral separation of these two graphene electrodes results in a lateral metal-semiconductor-metal junction with two asymmetric barriers but yet retains its ultrathin form of two-layer thickness. The rectification and diode behavior can be exploited in transistors, photodiodes, and light-emitting devices. We show that the device exhibits a rectification ratio up to 90 under a laser power of 1.37 μW at a bias voltage of ±3 V. We demonstrate that both the back-gate voltage and laser illumination can tune the rectification behavior of the device. Furthermore, the device can generate strong red electroluminescence in the WS area across the two graphene electrodes under an average flowing current of 2.16 × 10 A. This work contributes to the current understanding of the 2D metal-semiconductor heterojunction and offers an idea to obtain all-2D Schottky diodes by retaining the ultrathin device concept.
二维（2D）材料的超薄特性为制造比使用传统块状材料薄得多的器件提供了机会。在本文中，通过化学气相沉积法生长的单层 2D 材料被用于制造超薄全 2D 横向二极管。我们表明，将石墨烯电极置于 WS 单层的下方和上方，而不是同一侧，会导致具有两个不同肖特基势垒高度的横向器件。由于自然介电环境，底部石墨烯层被夹在 WS 和 SiO 衬底之间，其掺杂水平与与 WS 和空气接触的顶部石墨烯层不同。这两个石墨烯电极的横向分离导致具有两个不对称势垒的横向金属-半导体-金属结，但仍保留其两层厚度的超薄形式。该器件可以在晶体管、光电二极管和发光器件中利用整流和二极管特性。我们表明，该器件在偏置电压为±3 V 时，在 1.37 μW 的激光功率下，其整流比高达 90。我们证明了背栅电压和激光照射都可以调节器件的整流特性。此外，在平均电流为 2.16×10^-6 A 的情况下，器件可以在两个石墨烯电极之间的 WS 区域产生强烈的红色电致发光。这项工作有助于当前对 2D 金属-半导体异质结的理解，并提供了一种通过保留超薄器件概念来获得全 2D 肖特基二极管的思路。
