Electrical Engineering and Computer Sciences and §Berkeley Sensor and Actuator Center, University of California , Berkeley, California 94720, United States.
Nano Lett. 2014 Mar 12;14(3):1337-42. doi: 10.1021/nl4043505. Epub 2014 Feb 27.
The development of low-resistance source/drain contacts to transition-metal dichalcogenides (TMDCs) is crucial for the realization of high-performance logic components. In particular, efficient hole contacts are required for the fabrication of p-type transistors with MoS2, a model TMDC. Previous studies have shown that the Fermi level of elemental metals is pinned close to the conduction band of MoS2, thus resulting in large Schottky barrier heights for holes with limited hole injection from the contacts. Here, we show that substoichiometric molybdenum trioxide (MoOx, x < 3), a high work function material, acts as an efficient hole injection layer to MoS2 and WSe2. In particular, we demonstrate MoS2 p-type field-effect transistors and diodes by using MoOx contacts. We also show drastic on-current improvement for p-type WSe2 FETs with MoOx contacts over devices made with Pd contacts, which is the prototypical metal used for hole injection. The work presents an important advance in contact engineering of TMDCs and will enable future exploration of their performance limits and intrinsic transport properties.
开发低电阻源/漏接触过渡金属二卤化物（TMDC）对于实现高性能逻辑元件至关重要。特别是，对于使用 MoS2 制造 p 型晶体管，需要有效的空穴接触，MoS2 是一种典型的 TMDC。先前的研究表明，元素金属的费米能级被钉扎在 MoS2 的导带附近，因此空穴的肖特基势垒高度很大，从接触处的空穴注入有限。在这里，我们表明亚化学计量的三氧化钼（MoOx，x < 3），一种高功函数材料，作为 MoS2 和 WSe2 的有效空穴注入层。具体来说，我们通过使用 MoOx 接触来演示 MoS2 p 型场效应晶体管和二极管。我们还展示了具有 MoOx 接触的 p 型 WSe2 FET 的导通电流得到了显著提高，超过了使用 Pd 接触的器件，Pd 是用于空穴注入的典型金属。这项工作在 TMDC 的接触工程方面取得了重要进展，将能够进一步探索它们的性能极限和内在传输特性。
