When an electric field [E] is applied to a semiconductor, the free electrons and holes are drifted in opposite direction of the electric field., due to this a current is produced called drift current Vd.
Vd ∞ E
Vd = μ E
Where μ is called mobility.
Mobility is defined as the ratio of drift velocity to the applied electric field.
The total current in a semiconductor I = Ie + Ih
I = neμe EA + peμh EA
I = eEA [ nμe + pμh ]
μh – mobility of the holes (p)
In the case of intrinsic semiconductor, Number of free electrons [n] in the conduction band is equal to the number of holes [p] in the valence band.
∴ n = p = ni [intrinsic charge carrier concentration]
I = eEA [ni μe + ni μh ]
I = ni eEA [ μe + μh ]
The electrical conductivity of the intrinisic semiconductor is due to drifting action of electrons and holes is given by,
σi = ni e[ μe + μh ]
The electrical conductivity of the extrinsic semiconductors
σN = nN eμe
and σp = np eμh
| Read More Topics |
| Conduction in Semiconductors |
| Carrier concentration in metals |
| Energy distribution of electrons in metals |
