Question

The conductivity of an intrinsic semiconductor can be increased by:

• A. Heating the semiconductor
• B. Doping the semiconductor with electron rich impurity
• C. Doping the semiconductor with electron deficient impurity
• D. Cooling the semiconductor

Answer 1

Answer: (A), (B), (C)

Doping the semiconductor with electron deficient impurity

Semiconductors are solids with conductivity that is intermediate between conductors and insulators which lies in the range ${10}^{-6}\text{to}{10}^{4}oh{m}^{-1}{m}^{-1}$.

The conduction of electricity for semiconductors depends on the temperature.
At normal temperatures or higher temperature, some electrons are thermally excited from the valence band to the conduction band. So, their electrical conductivity will increase with rise in its temperature.

If a semidonductor is cooled to absolute zero $\left(0K\right)$ the electrons occupy their lowest possible energy levels. The conduction band is empty because at very low temperature electrons cannot jump from the valence band to conduction band. Thus, the conductivity will decreased to zero.

The intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties is called dopping.
Doping can be carried out using electron rich impurities and electron deficient impurity. Both will increase the conductivity of semiconductors.