12/04/2021

Mobility

 

The conductivity arises form mobile charge carriers of the semiconductor. 

Types of matter

Mobile charge carriers

Metal

Electrons

Ionized gas

Electrons & positive charged ions

Electrolyte

Position ions and negative ions

 

Mobility

  • It is defined as the magnitude of the drift velocity per unit electric field.

       µ = Vd / E ………. ( 1 )

  • Where µ = Mobility
  • Vd = Drift velocity ( meter / second )
  • E = Electric field  ( volt / meter )

The unit of mobility is = ( meter / second ) / ( volt / meter )

                                       = meter2 / volt – second

The mobility is positive. The drift velocity is also given by

Vd = eτE / m……………… ( 2 )

Where τ = Average collision time of electrons

            e = Charge

             m = mass of electrons

from equation ( 1 ) and ( 2 )

µ = eτE / mE

µ = eτ / m

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