InSe Schottky Diodes Based on Van Der Waals Contacts

2D 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.