Abstract
Abstract2D semiconductors are excellent candidates for next‐generation electronics and optoelectronics thanks to their electrical properties and strong light‐matter interaction. To fabricate devices with optimal electrical properties, it is crucial to have both high‐quality semiconducting crystals and ideal contacts at metal‐semiconductor interfaces. Thanks to the mechanical exfoliation of van der Waals crystals, atomically thin high‐quality single‐crystals can easily be obtained in a laboratory. However, conventional metal deposition techniques can introduce chemical disorder and metal‐induced mid‐gap states that induce Fermi level pinning and can degrade the metal‐semiconductor interfaces, resulting in poorly performing devices. In this article, the electrical contact characteristics of Au–InSe and graphite–InSe van der Waals contacts, obtained by stacking mechanically exfoliated InSe flakes onto pre‐patterned Au or graphite electrodes without the need for lithography or metal deposition is explored. The high quality of the metal‐semiconductor interfaces obtained by van der Waals contact allows to fabricate high‐quality Schottky diodes based on the Au–InSe Schottky barrier. The experimental observation indicates that the contact barrier at the graphite–InSe interface is negligible due to the similar electron affinity of InSe and graphite, while the Au–InSe interfaces are dominated by a large Schottky barrier.
Highlights
Two-dimensional (2D) semiconductors, which hold a great promise for future electronic and optoelectronic applications,[1,2,3] have motivated a surge of interests of the scientific community
We found that the Au-Indium selenide (InSe) interface is dominated by a large Schottky barrier that we estimate to be approximately 460 meV while the Gr-InSe interface shows a negligible barrier
We leave a spatial gap between the two electrodes that can accommodate an InSe flake that can be transferred in the gap contacting the two Gr flakes
Summary
Two-dimensional (2D) semiconductors, which hold a great promise for future electronic and optoelectronic applications,[1,2,3] have motivated a surge of interests of the scientific community. InSe has gained widespread attention due to its ultrahigh electron mobility (with reported values of ~104 cm2v-1s-1 at 4 K and ~4000 cm2v-1s-1 at room temperature37), excellent mechanical properties (the reported Young’s modulus of ~20 GPa makes InSe one of the most flexible 2D materials38) and super strong light-matter interaction (responsivity up to 107 A/W and detectivity up to 1015 Jones have been reported 39).[37,38,39,40,41] We found that the Au-InSe interface is dominated by a large Schottky barrier that we estimate to be approximately 460 meV while the Gr-InSe interface shows a negligible barrier (smaller than 100 meV) We exploit this difference in the barriers to fabricate Schottky diodes based on asymmetrically contacted InSe flakes by van der Waals stacking, which does not require any lithographic process or metallization on 2D semiconductors. Our findings demonstrate a new strategy to reach good Schottky diodes by van der Waals stacking based on 2D semiconductors and pave the way for future electronic and optoelectronic applications
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