Field-Effect Transistors Built from All Two-Dimensional Material Components

Abstract

We demonstrate field-effect transistors using heterogeneously stacked two-dimensional materials for all of the components, including the semiconductor, insulator, and metal layers. Specifically, MoS2 is used as the active channel material, hexagonal-BN as the top-gate dielectric, and graphene as the source/drain and the top-gate contacts. This transistor exhibits n-type behavior with an ON/OFF current ratio of >10(6), and an electron mobility of ∼33 cm(2)/V·s. Uniquely, the mobility does not degrade at high gate voltages, presenting an important advantage over conventional Si transistors where enhanced surface roughness scattering severely reduces carrier mobilities at high gate-fields. A WSe2-MoS2 diode with graphene contacts is also demonstrated. The diode exhibits excellent rectification behavior and a low reverse bias current, suggesting high quality interfaces between the stacked layers. In this work, all interfaces are based on van der Waals bonding, presenting a unique device architecture where crystalline, layered materials with atomically uniform thicknesses are stacked on demand, without the lattice parameter constraints. The results demonstrate the promise of using an all-layered material system for future electronic applications.

Graphene Oxide as a Promising Hole Injection Layer for MoS2-Based Electronic Devices

“…Such architectures have been used recently to fabricate MoS 2 FETs with graphene contacts. 24 We point out that, experimentally, it could be easier to fabricate a device based on an "inverted" architecture, by depositing GO layers on metal contacts using lithography and etching techniques, as recently demonstrated by Roy et al 24 We highlight that the role of GO in MoS 2 FETs is not limited to that of obtaining p-FETs. As depicted in Figure 1c, GO can be used as a substrate to control p-type doping in MoS 2 as evidenced from our calculations.…”

Visibility of two-dimensional layered materials on various substrates

“…For instance, all-2D-FETs as well as 2D heterojunction interlayer tunneling FETs have recently been investigated. 20,21 However, due to a lack of appropriate epitaxial realizations, 2D heterojunctions have to be fabricated by stacking different 2D materials on top of each other using, e.g., the transfer method proposed by Dean and coworkers. 22 In turn, this makes the use of intermediary substrates necessary that enable an unambiguous identification of the respective 2D materials with optical microscopy.…”

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors

“…To date, various innovative strategies to reduce the contact resistance such as use of 3 graphene contacts 3,[18][19][20] and phase-engineering, 21,22 are still deficient as they do not offer true ohmic contact behavior or have insufficient thermal stability. Nearly barrier-free contacts to MoS 2 have been achieved by using graphene as contact electrodes because the Fermi level of graphene can be effectively tuned by a gate voltage to align with the conduction band minimum ( CBM ) of MoS 2 , which minimizes the Schottky barrier height (SBH).…”