Two dimensional Green's function solution of threshold for junction less field effect transistors at low drain voltage

Abstract

The threshold voltage is an important device and circuit parameter of any FET structure. In this paper, closed form analytic expressions are derived which determine the dependence of the threshold voltage of DGJLFETs on device dimensions, and the drain voltage. The depletion approximation and the two dimensional Green's function are used to determine the terminal behavior of the device. The model includes the effect of the depletion in the gate-drain spacing. The threshold condition is reached when the depletion layers from the two sides cross i.e., when the channel pinches off. The widening of the depletion layer under sub-threshold condition, and the movement of the pinch-off point with the drain voltage are calculated. Finally, the shift in threshold voltage and DIBL with the gate length is determined. We can also determine the potential distribution within the device. To verify our calculations, the analytical results are compared with 2-D numerical simulations. The agreement is especially good at low drain voltages.