Impact ionization induced dynamic floating body effect in junctionless transistors

Subthreshold Swings, SSs, smaller than theoretical ‘ln(10)kT/q’ are observed in nanowire junctionless (JL) and inversion mode (IM) MuGFETs. The low SS is attributed to the floating body effect in the channel, which is initiated by impact ionization. Comparing with IM devices, decreased drain voltage (Vd) is required for the generation of steep subthreshold slopes in JL devices and the floating body is relatively dynamic. In both JL and IM MuGFETs the floating body effect is suppressed for narrow devices, which indicates this effect is geometry dependent. Moreover, it shows that the short channel JL devices with enhanced electric field can exhibit steep subthreshold slopes at lower Vd. It gives another option to decrease the supply voltage (Vdd) for low power applications of JL devices.

► Steep SS in JL devices are observed.
► A positive loop turns on the device at lower Vt.
► The impact ionization in short channel JL devices is more pronounced.