Investigation of the Subthreshold Swing in Vertical Tunnel-FETs Using and Anneals

This paper analyzes both experimentally and by simulation the impact of traps on the transfer characteristics of tunnel-FETs (TFETs). The interface trap density in vertical heterojunction TFETs is varied by annealing in hydrogen or deuterium ambient. We show that a high-interface trap density (~2×10 12 /cm 2 ) results in a peak current in the device transfer characteristic at low-gate bias due to surface generation of carriers. The passivation of interface traps to state-of-the-art densities near 1-2×10 11 /cm 2 reduces this peak, but improves only marginally the overall subthreshold swing, indicating that the trap-assisted tunneling responsible for the swing degradation is mainly occurring through bulk traps in these devices.