Direct determination of threshold condition in DG-MOSFETs from the gm/ID curve

In this work we apply the current-based threshold voltage definition (equality between the drift and diffusion components of drain current) to intrinsic symmetric double-gate MOSFETs. We show that the half maximum point of the gm/ID (transconductance-to-current ratio) curve in the linear region corresponds exactly to the condition IDdrift = IDdiff when mobility variation is neglected. Numerical simulations show that the threshold voltages determined from the gm/ID curve and from the IDdrift = IDdiff condition differ by about ϕt/2 (one half of the thermal voltage) when considering realistic mobility variations. Simulation results show that the threshold voltages determined with the gm/ID procedure are close to those obtained with the Y (=ID/gm) function method for a considerable range of silicon film thicknesses, channel lengths, and temperature values. The current-based procedure has also been successfully applied experimentally to a FinFET over a wide temperature range.