On the asymmetry of the DC and low-frequency noise characteristics of vertical nanowire MOSFETs with bulk source contact

Abstract

In this work, the impact of switching the source and drain on the low-frequency noise of Gate-All-Around (GAA) Vertical Nanowire (VNW) n-and pMOSFETs fabricated on bulk silicon wafers is investigated. Switching the role of the electrodes results in an increase in the absolute value of the threshold voltage, a higher subthreshold slope and maximum transconductance. For the p-channel devices, significantly lower 1/f noise is observed in reverse operation compared with the normal forward configuration. Considering the mobility fluctuations origin of the 1/f noise, this indicates a pronounced impact of the choice of the source/drain contact on the conduction in the p-type silicon nanowires. On the other hand, little effect on the noise behaviour has been found from the in-situ boron doping density in the NWs. For the n-channel FETs, qualitatively similar results have been obtained with respect to the 1/f noise PSD. At the same time, the dominant flicker noise mechanism changes from Ag domi-nated in F operation to rather delta n in R mode.