On the performance limits for Si MOSFET's: A theoretical study

Performance limits of silicon MOSFET's are examined by a simple analytical theory augmented by self-consistent Schrodinger-Poisson simulations, The on -current, transconductance, and drain-to-source resistance in the ballistic limit (which corresponds to the channel length approaching zero) are exami ned. The ballistic transconductance in the limit that the oxide thickness a pproaches zero is also examined. The results show that as the channel lengt h approaches zero (which corresponds to the ballistic limit), the on-curren t and transconductance approach finite limiting values and the channel resi stance approaches a finite minimum value, The source velocity can be as hig h as about 1.5 x 10(7) cm/s. The limiting on-current and transconductance a re considerably higher than those deduced experimentally by a previous stud y of MOSFET's with channel lengths greater than 0.2 mu m. At the same time, the transconductance to current ratio is substantially lower than that of a bipolar transistor.