Single Defect Discharge Events in Vertical-Nanowire Tunnel-FETs

In this paper, we investigate the single defect discharge events in Ge-source n-type vertical nanowire tunnel field effect transistors, by monitoring the relaxation phase which follows bias temperature instability (BTI) stress. Threshold voltage shift induced by single discharge events follows a bimodal Weibull distribution, with the location parameter of the second mode being significantly higher than the first one. Both modes are temperature independent. Based on TCAD simulations, we propose that the second mode is associated with defects located at the source/channel junction close to the channel/oxide interface, while the first mode is ascribed to oxide traps far from the source/channel junction. Although present in smaller numbers, such traps with a larger average impact on the device characteristics are expected to dominate the BTI-induced variability in a large population of nanoscale devices for realistic applications.