Bias-Independent Subthreshold Swing in Nanoscale Cold-Source Field-Effect Transistors by Drain Density-of-States Engineering

We report a strategy to design nanoscale cold-source field-effect transistors (CS-FETs) with bias-independent sub-60 mV/dec subthreshold swing (SS). By first-principles calculations and quantum-transport simulations, we reveal that the energy alignment of density of states (DOS) between the drain and source electrodes is critical to achieving bias-independent SS. By defining "gate window", we propose a device model to demonstrate how similar slopes of the drain DOS falling into the gate window can stabilize the SS under different bias. This study underscores the significance of drain DOS engineering in the design of CS-FETs with bias-independent SS for portable electronic applications.