Unraveling Subthermionic Transport in One-Dimensional van der Waals Isolated-Band FETs

A one-dimensional (1D) van der Waals material system offers an ideal platform for designing innovative devices and mitigating power consumption challenges in integrated circuits. Yet, the relationship between their electronic structure, particularly isolated-band features, and the intrinsic subthermionic transport mechanisms in 1D isolated-band-source field-effect transistors (IBS-FETs) remains underexplored. Using first-principles quantum transport simulations, we elucidated the structure-performance relationship of 1D IBS-FETs with a gate length of 7.3 nm. Our findings revealed that the dominant current mechanisms, whether tunneling or thermionic emission, are governed by isolated-band features (bandwidth and sub-bandgap), while key electronic structure parameters (bandgap and electron effective mass) shaping subthreshold and superthreshold characteristics were explicitly identified. Specifically, 1D IBS-FETs (SbSBr, SiS₂, SiSe₂, Se, and Te) meet International Technology Roadmap for Semiconductors requirements for high-performance and low-power devices. This study clarifies the intrinsic subthermionic electronic transport mechanisms in 1D IBS-FETs, providing critical theoretical insights for designing low-power, high-speed electronic switches.