An intrinsic semiconductor behaves as an insulator at-

The correct answer is option 4) i.e. 0 K

CONCEPT:

• Intrinsic semiconductor: An intrinsic semiconductor is a pure semiconductor without any dopant species present in it.
  •  Since there are no impurities present in it, the number of free electrons equals the number of holes in an intrinsic semiconductor.
• Energy band gap: It is the distance between the valence band and conduction band of material.
  • Electrons in the conduction band are responsible for current.
  • The gap between the valence band and conduction band represents the minimum energy required by an electron in the valence band to jump to the conduction band.

EXPLANATION:

• In an intrinsic semiconductor, conduction occurs only when the electrons in the valence band can move to the conduction band.
• To cross over the energy gap between the valence band and conduction band, the electrons will require some amount of energy.
• Hence, at higher temperatures, the electrons will gain energy and jump into the conduction band.
• 0 K is also known as absolute zero. It is the temperature at which the particles in a substance are motionless.
• At 0 K, the electrons will not have the energy to move into the conduction band.
• Thus, there is no conductivity at 0 K in intrinsic semiconductors and it behaves as an insulator.