High-Performance Flexible Vertical Asymmetric-Contact WS₂ Schottky Diodes with Ultrahigh Current Density and...

The relentless drive toward next-generation wearable technologies, soft robotics, and the Internet of Things (IoT) has created a critical demand for high-performance electronic components that are mechanically flexible and robust. However, the development of two-dimensional (2D) material-based diodes that simultaneously achieve high current rectification, large forward current density, excellent mechanical compliance, and long-term operational stability remains a formidable challenge. Here, we report the fabrication and characterization of an innovative vertical Schottky diode based on a few-layer tungsten disulfide (WS₂) channel with asymmetric Ag and Au contacts on a flexible substrate. By engineering a significant disparity in the Schottky barrier heights at the two metal-semiconductor interfaces, we demonstrate a device with a suite of state-of-the-art performance metrics. These include an exceptional current rectification ratio exceeding 7 × 10⁵, an ultrahigh forward current density approaching 6 × 10⁴ A/cm², and a near-ideal ideality factor of 1.66. Temperature-dependent measurements reveal that charge transport is dominated by thermionic emission in high-quality devices, while devices with higher defect densities exhibit an anomalous negative temperature coefficient, a behavior attributed to a trap-assisted tunneling (TAT) transport mechanism. The device also exhibits outstanding mechanical resilience, maintaining stable electrical characteristics after numerous bending cycles and at aggressive bending radii as small as 5 mm. Furthermore, it demonstrates excellent ambient stability, with negligible performance degradation over one month. These findings establish a new benchmark for flexible 2D diodes and suggest that the vertical asymmetric contact architecture provides a viable and powerful strategy for realizing high-frequency, low-power flexible electronics for advanced wearable systems.