A piece of germanium is cooled from room temperature to 100 K. Its conductivity will
Right Answer is:
A piece of germanium is cooled from room temperature to 100 K. Its conductivity will decrease.
Intrinsic conductivity:- Semiconductors are conductive beyond a certain temperature level as valence electrons are released from their chemical bonds with increasing temperatures and thus reach the conduction band (intrinsic conductivity). They become conduction electrons that are able to move freely through the crystal lattice (i.e. electron conduction).
On the other hand, also the resulting hole inside the valence band can move through the semiconductor material since a neighboring electron can advance to the hole. Holes thus contribute equally to conductivity (hole conduction). Since every free electron creates a hole within undisturbed pure semiconductor crystals both types of charge carriers equally exist.
For every temperature, there exists an equilibrium state with a certain number of free holes and free electrons. The number of free electron-hole pairs increases with rising temperature.
As the temperature is decreased to 100 K, therefore, less number of the electron-hole pair will be generated hence the conductivity of the semiconductor will decrease.