NREL Theory Establishes a Path to High-Performance 2D Semiconductor Devices
April 27, 2016 | NRELEstimated reading time: 2 minutes

Researchers at the Energy Department's National Renewable Energy Laboratory (NREL) have uncovered a way to overcome a principal obstacle in using two-dimensional (2D) semiconductors in electronic and optoelectronic devices.
2D semiconductors such as molybdenum disulfide are only a few layers thick and are considered promising candidates for next-generation devices. Scientists first must overcome limitations imposed by a large and tunable Schottky barrier between the semiconductor and a metal contact. The barrier, at the metal/semiconductor junction, creates an obstacle for the flow of electrons or holes through the semiconductor.
The NREL team discovered that the height of the Schottky barrier can be adjusted-or even made to vanish-by using certain 2D metals as electrodes. Such adjustments are not possible with conventional three-dimensional metals because of a strong Fermi level pinning (FLP) effect occurring at the junction of metal and semiconductor, due to electronic states in the semiconductor band gap that are induced by the metal. Increasing the flow of electrons or holes through a semiconductor reduces power losses and improves the device performance.
The NREL theorists considered a family of 2D metals that could bind with the 2D semiconductors through van der Waals interaction. Because this interaction is relatively weak, the metal-induced gap states are suppressed and the FLP effect is negligible. This means that the Schottky barrier becomes highly tunable. By selecting an appropriate 2D metal/2D semiconductor pair, one can reduce the barrier to almost zero (such as H-NbS2/WSe2 for hole conduction).
They noted that using a 2D metal as an electrode would also prove useful for integrating into transparent and flexible electronics because the 2D metal is also transparent and flexible. They also noted that the junction of 2D metal and 2D semiconductor is atomically flat and can have fewer defects, which would reduce carrier scattering and recombination.
The work by Yuanyue Liu, Paul Stradins, and Su-Huai Wei, "Van der Waals metal-semiconductor junction: weak Fermi level pinning enables effective tuning of Schottky barrier," appears in the new issue of Science Advances.
The trio of researchers predicts that hexagonal phase of niobium disulfide (NbS2) is the most promising for hole injection into a 2D semiconductor, and heavily nitrogen-doped graphene can enable efficient electron injection.
This research was funded by the Department of Energy's Office of Energy Efficiency and Renewable Energy. The work used computational resources at NREL and the National Energy Research Scientific Computing Center.
NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.
Suggested Items
Indium Acquires SAFI-Tech to Advance Low-Temperature Soldering Technology
10/03/2023 | Indium CorporationIndium Corporation, an international electronics materials refiner, smelter, manufacturer, and supplier, is proud to announce the acquisition of SAFI-Tech, a metal microcapsule technology innovator specializing in supercooling technology.
IDTechEx Explores How EMI Shielding is Enabling Compact Electronics
09/26/2023 | PRNewswireIt is no secret that electronic devices are becoming increasingly compact, with greater functionality contained in smaller volumes.
Conecsus Metals Mexico to Exhibit Waste Recycling Solutions at SMTA Guadalajara Expo & Tech Forum
09/26/2023 | Conecsus Metals MéxicoConecsus Metals México, an innovative environmental technology and recycling company, will exhibit at the SMTA Foro Tecnico & Expo, Guadalajara, Jalisco, México, on Wednesday, October 25, 2023, beginning at 11:00 a.m.
Trouble in Your Tank: Processes to Support IC Substrates and Advanced Packaging, Part 4
09/28/2023 | Michael Carano -- Column: Trouble in Your TankIn a previous column, the critical process of desmear and its necessity to ensure a clean copper surface connection was presented. Now, my discussion will focus on obtaining a void-free and tightly adherent copper plating deposit on these surfaces. After the desmear process, the task is to insure a continuous, conductive, and void-free deposit on the via walls and capture pad. Today, there are several processes that can be utilized to render vias conductive.
Path Robotics Announces Next Chapter in Delivering Fully Autonomous Manufacturing Systems with AF-1
09/11/2023 | PRNewswirePath Robotics, the market leader of truly autonomous welding robotic systems, announced their next chapter in delivering fully autonomous manufacturing systems with their new Autonomous Fit-up robotic system ("AF-1"), a ground-breaking robotic cell capable of performing both fit-up and welding of metal parts.