Question

In an intrinsic semiconductor, conductivity is
(A) Low at room temperature
(B) Average
(C) High at room temperature
(D) Zero at room temperature

Answer 1

Hint : A semiconductor is material whose conductivity is greater than that of an insulator but less than that of conductor. Semiconductors which are free from impurities are called intrinsic semiconductors. Here the number of holes and electrons are the same. They are also called n doped semiconductors or i-type semiconductors.

Complete step by step solution:
In characteristic semiconductors, the number of holes and electrons are the same. Thus, at room temperature, no free electrons are accessible for conduction. When the temperature is increased, the covalent bonds will break and electrons will be liberated, every electron will abandon an opening and catch another opening the cycle will proceed and charge moves through characteristic semiconductor. Along these lines, its conductivity increments with temperature.

Consequently, characteristic semiconductor conductivity is low at room temperature.

Additional Information:
When the temperature of the intrinsic semiconductor is zero kelvin it will behave as an insulator. When the temperature is increased the electrons move from valence band to conduction band. Valence Band: The energy band including the energy levels of valence electrons is known as the valence band. It is the most occupied energy band. It permits the electrons in the valence band to bounce into the conduction band on getting any external energy energy.
Conduction Band: It is the least occupied band that incorporates the energy levels of positive (openings) or negative (free electrons) charge transporters. It has directing electrons bringing about the progression of current. The conduction bands have high energy levels and are by and large unfilled.

Note:
Fermi level is present between valence band and conduction band and is the highest occupied molecular orbital at absolute zero temperature. They do not interact with each other and when the temperature rises above absolute zero charge carriers will begin to occupy states above fermi level.