Abstract
Physical and electronic asymmetry plays a crucial role in rectifiers and other devices with a directionally variant current-voltage (I-V) ratio. Several strategies for practically creating asymmetry in nanoscale components have been demonstrated, but complex fabrication procedures, high cost, and incomplete mechanistic understanding have significantly limited large-scale applications of these components. In this work, we present density functional theory calculations which demonstrate asymmetric electronic properties in a metal-semiconductor-metal (MSM) interface composed of stacked van der Waals (vdW) heterostructures. Janus MoSSe has an intrinsic dipole due to its asymmetric structure and, consequently, can act as either an n-type or p-type diode depending on the face at the interior of the stacked structure (SeMoS-SMoS vs. SMoSe-SMoS). In each configuration, vdW forces dominate the interfacial interactions, and thus, Fermi level pinning is largely suppressed. Our transport calculations show that not only does the intrinsic dipole cause asymmetric I-V characteristics in the MSM structure but also that different transmission mechanisms are involved across the S-S (direct tunneling) and S-Se interface (thermionic excitation). This work illustrates a simple and practical method to introduce asymmetric Schottky barriers into an MSM structure and provides a conceptual framework which can be extended to other 2D Janus semiconductors.
Highlights
Physical and electronic asymmetry plays a crucial role in devices like rectifiers [1,2,3,4], which produce current-voltage (I - V) outputs and vary directionally depending on the applied bias
One strategy to produce current asymmetry is through metal-semiconductor-metal (MSM) structures composed of two metal-semiconductor (MS) junctions with distinct Schottky barriers connected back to back [5, 6]
Fermi level pinning (FLP) caused by defects is the most universal [7], can significantly hinder effective control of Schottky barriers at the contact, and requires complicated treatment of the bulk metal to avoid [11]
Summary
Physical and electronic asymmetry plays a crucial role in devices like rectifiers [1,2,3,4], which produce current-voltage (I - V) outputs and vary directionally depending on the applied bias. FLP caused by defects is the most universal [7], can significantly hinder effective control of Schottky barriers at the contact, and requires complicated treatment of the bulk metal to avoid [11]. To overcome these obstacles, we propose a new class of MSM structure fabricated by stacking two-dimensional (2D) Janus materials and 2D metals.
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