Velocity Saturation after Pinch Off??

Hi friends,

At the moment, I'm studying channel length modulation (CLM) in
MOSFET. Simply speaking, when a n-channel transistor is in
saturation region and Vds is increased with fixed Vgs, Id increases
linearly due to CLM. This is because the depletion region depth of
the reverse-bias diode across the drain and the substrate gets
larger and larger with increasing Vds, causing shorter effective
length ~ Leff = 1/(1+Lamda*Vds).

My questions are:
(1) As the effective length of transistor decreases, would it cause velocity saturation? :?:

(2) If so, would it in turn make Id constant with increasing Vds because the effect of velocity saturation compensates the effect of channel length modulation? :?:

Channel length modulation: Id increases cos Leff decreases =>
larger electric field (exceed critical electric field) =>
mobility decreases (velocity saturation) => Id decreases =>
Total effect: Id keeps constant

Any comment would be very appreciated ~

Will

hi,

Velocity saturation occurs in both the long channel and short channel devices. we are in era of short channel devics (feature size≤1um). velocity saturation takes place much earlier than the expected pinch off as E(critical) between source and drain establishes at very low VDS. E=dV/dx

therefore, the conventional channel length modulation concept may not be exactly applicable, in short channel devices, as given in the books for long channel devices.