Direct determination of threshold condition in DG-MOSFETs from the g_m/I_D curve

摘要

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 g_m/I_D (transconductance-to-current ratio) curve in the linear region corresponds exactly to the condition I_(Ddrift) =I_(Ddriff) when mobility variation is neglected. Numerical simulations show that the threshold voltages determined from the g_m/I_D curve and from the I_(Ddrift) =I_(Ddriff) condition differ by about Φ_t/2 (one half of the thermal voltage) when considering realistic mobility variations. Simulation results show that the threshold voltages determined with the g_m/I_D procedure are close to those obtained with the Y (=I_D/g_m~(-2)) 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.