In conductors the valence and conduction bands overlap.

Substances with energy gap of the order of 10 eV are insulators.

The resistivity of a semiconductor increases with increase in temperature.

The conductivity of a semiconductor increases with increase in temperature.

widens the depletion zone

increases the potential difference across the depletion zone

increases the number of donors on the n side

decreases the electric field in the depletion zone.

amplification

rectification

stabilisation

producing oscillations in an oscillator.