Guiding charge injection in Schottky-barrier transistors through the spatial Fermi-level gradients of heterogeneous bimetallic systems

Abstract

A heterogeneous bimetallic system (HBS), composed of two metallic thin films with inherently different Fermi levels, is potentially usable for the fine tuning of interfacial charge dynamics. Here, we propose a viable methodology for adjusting the turn-on voltage (V_to) of Schottky-barrier TFTs (SB-TFTs) based on new insights into the utilization of the physical properties of metallic materials. HBS-based thin films are demonstrated to provide a designable workfunction at a structural level. The acquired spatial gradients of the Fermi level, formed in the HBS, are considered a critical factor for achieving the structurally designable workfunction. During device testing, a significant correlation is observed between the V_to of SB-TFTs and the workfunction of their HBS-based source–drain (SD) electrodes. The ability to tailor the V_to property through the HBS strategy is attributed to the variation in workfunction of the HBS-based SD electrodes, which modulates the charge injection across the Schottky barrier. The V_to variation is extensively investigated by exploring various structural aspects of the HBS-based SD electrodes. Lastly, the HBS strategy enables clear off-states in both n-type and p-type SB-TFTs and their balanced electrical performances, through which a complementary inverter is successfully demonstrated.