Correct Answer - Option 4 : increase
Explanation:
Current in a material can be expressed as:
I = NqAvd
Where
N = Carrier concentration
q = electrons charge (magnitude)
A = cross-section area
The current density (J) will be:
\(J = \frac{I}{A} = Nq{v_d}\) ---(1)
Also, J = σ E ----(2)
σ = conductivity
E = Electric field
J = Current density
vd = μ E ----(3)
μ = mobility of carriers
E = Electric field
Analysis:
On using equation (1), (2) & (3) we get,
J = NqVd = NqμE = σE
⇒ σ = Nqμ
So as conductivity is directly proportional to the mobility of ions and the number of EH pair ions.
The conductivity of an intrinsic semiconductor depends upon the number of hole electron pairs and mobility. The number of hole electron pairs increases with an increase in temperature, while its mobility decreases. However, the increase in hole electron pairs is greater than the decrease in their mobility.
So with an increase in temperature, conductivity in semiconductors also increases.
Hence option (4) is the correct answer.