  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.
