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.
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