Impact of Transport Anisotropy on the Performance of van der Waals Materials-Based Electron Devices

Layered van der Waals (vdW) semiconductors have emerged as preferred materials for building nextgeneration electronic devices, such as diodes and fieldeffect transistors (FETs), because of their capability of providing high mobility at the nanometer-scale thickness, as well as their flexibility and pristine interfaces. However, the inherent “vdW gaps” in these materials lead to much larger cross-plane resistivity, with respect to in-plane resistivity, thereby forming intriguing transport anisotropy. In this article, using extensive numerical simulations, it is found that this anisotropy introduces anomalous current transport behavior in vdW-based electron devices in which the current conducts in both the in-plane and cross-plane directions, including stacked heterojunction diodes and thin-film transistors (TFTs). Our study reveals for the first time that transport anisotropy degrades the performance of these devices, especially when devices are scaled (<; 0.6 μm) and/or relatively thicker materials (>4 nm) are used. Potential solutions to alleviate degradation are discussed as well.