As shown in the channel length of a saturated nMOSFET is reduced by the amount DL. This reduction stems from the widening of the SCL associated with the junction formed by the p2 body and the n+...

As shown in the channel length of a saturated nMOSFET is reduced by the amount DL. This reduction stems from the widening of the SCL associated with the junction formed by the p2 body and the n+ drain. Because doping is asymmetrical (ND @ NA), the SCL extends mostly into the lightly-doped body region. Adapting Eq. (1.45) to the present case gives ΔL is the junction’s built-in potential, and V is the junction’s voltage drop right at the drain end of the channel, or V 5 VOV 2 VDS. (a) Given that with the overdrive voltage VOV 5 1 V a certain nMOSFET yields ID 5 210 A at VDS 5 2 V, and ID 5 220 A at VDS 5 4 V, what are the values of and k? Hint: consider the ratio of the two currents. (b) Assuming a process with bulk doping NA 5 1016 cm23 , polysilicon gate doping ND 5 1020 cm23 , and k5 50 A/V2 , what are the values of DL in the two cases? (c) Exploiting the fact that ID is inversely proportional to L 2 DL, estimate L. What is the value of W?