Mechanisms of forward current transport in vertical nanoscale devices: insights and applications

Abstract Current transport at metal/semiconductor interface becomes critical to determining ultimate limit in performance of two-dimensional (2D) electronic devices. In this work, we study output characteristics as well as carrier transport of the vertical Schottky-contact 2D transistors and diodes, by experimental measurements and detailed TCAD simulations. Device output current under the forward bias is primarily attributed to thermionic emission (TE) mechanism, then tunneling occurs and becomes the dominant interfacial charge transport in the few-layered MoS 2 transistors. While shrinking the vertical channel length from 20 nm to 3.6 and increasing the applied voltage, tunneling ratio rises above 90% for the sub-5 nm scale, indicating the dominated tunneling mechanism. Simultaneously, the Schottky diode loses its rectification ability. Noticeably, Fowler–Nordheim tunneling (FNT) mechanism cannot be accurately identified through the linear slope of ln( I / V 2 ) versus 1/ V (FN-relation) of output current under high electric field, due to the co-existing thermionic current that displays a linear-like feature in the FN-relation plots. The transition from TE to FNT and direct tunneling (DT) regimes can be identified by analyzing the output current components and FN-relation of tunneling current. These results can be employed to understand physical insights and transport limitations of the nanoscale electronics, and to optimize the device design and performance for their ultra-scaled, low-power applications.