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Sunday, March 12, 2017

#366 Velocity saturation

A brief comment related to previous blog on the mobility of charge carriers. Velocity of charge carriers moving in semiconductor under the influence of electric field increases with the increasing electric field, but then saturates at certain maximum value. Saturation occurs because of the excessive scattering of charge carriers drifting in semiconductor lattice with very high velocity enforced by the very high electric field.


Saturation velocity and electric field at which it is reached are material parameters which are different in different single-crystal semiconductors due to the different spatial distribution of atoms in the crystal lattice in different semiconductors. Interestingly, high saturation velocity does not have to coincide with high electron mobility featured by any given semiconductor. For instance, silicon (Si), featuring significantly lower electron mobility than gallium arsenide (GaAs), displays higher saturation velocity than the latter.


In general, values of saturation velocity and values of the electric field at which it saturates are very good predictors of the ability of semiconductor material to operate under the very high electric field. Keep in mind that the very high electric field in ultra-small geometry devices may occur at relatively low bias voltages.


Posted by Jerzy Ruzyllo at 10:49 AM | Semiconductors | Link is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.

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