Degradation of electrical performance of few-layer tungsten selenide-based transistors

Semiconducting transition-metal dichalcogenides (TMDs) have garnered significant interest due to their unique structures and properties, positioning them as promising candidates for novel electronic and optoelectronic devices. However, the performance of TMDs-based devices is hampered by the suboptimal quality of metal electrodes contacting the atomically thin TMDs layers. Understanding the mechanisms that influence contact quality is crucial for advancing TMDs devices. In this study, we investigated the conductive properties of tungsten selenide (WSe₂)-based devices with different film thicknesses. Using the transmission line method, a negative correlation between contact resistance and film thickness in multi-electrode devices was revealed. Additionally, repeatability tests conducted at varied temperatures indicated enhanced device stability with increasing film thickness. Theoretical analysis, supported by thermionic emission theory and thermal simulations, suggests that the degradation in electrical properties is primarily due to the thermal effect at the contact interface. Furthermore, we found that van der Waals contacts could mitigate the thermal effect through a metal transfer method. Our findings elucidate the critical role of contact resistance in the electronic performance of 2D material-based field-effect transistors (FETs), which further expands their potential in the next generation of electronic and optoelectronic devices.

Graphical Abstract