Velocity overshoot
Encyclopedia
Velocity overshoot is a result of transit times of a charge carrier
going from source to drain being smaller than the time required to emit an optical phonon. The velocity therefore exceeds the saturation velocity
, which leads to faster field-effect transistor
switching. This notion is utilized when the gate length is reduced to increase the switching speed.
Charge carriers in semiconductors
There are two recognized types of charge carriers in semiconductors. One of them is electrons, which carry negative electric charge. In addition, it is convenient to treat the traveling vacancies in the valence-band electron population as the second type of charge carriers, which carry a positive...
going from source to drain being smaller than the time required to emit an optical phonon. The velocity therefore exceeds the saturation velocity
Velocity saturation
In semiconductors, when a strong enough electric field is applied, the carrier velocity in the semiconductor reaches a maximum value, saturation velocity. When this happens, the semiconductor is said to be in a state of velocity saturation...
, which leads to faster field-effect transistor
Field-effect transistor
The field-effect transistor is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with...
switching. This notion is utilized when the gate length is reduced to increase the switching speed.