Question

The charge carriers in a p-type semiconductor are:
(A). Electrons only
(B). Holes only
(C). Holes in larger number and electrons in smaller number
(D). Holes and electrons in equal number

Answer 1

Hint: p-type semiconductors have trivalent impurity and because of this we have excess number of holes in this type of semiconductor. The current that flows in this type of conductors is due to the movement of holes inside the material.

Complete step by step answer:
The material which has conductivity in the range between that of conductors and insulators is called semiconductor. Semiconductors are of two types – one is intrinsic semiconductor and the other is extrinsic semiconductor.
Intrinsic semiconductors are pure elements such as silicon.
Extrinsic semiconductors made by doping other impurities to improve its conductivity.
Extrinsic semiconductors are of n-type or p-type depending on the property of the impurity. In n-type semiconductor we add pentavalent impurity and in p-type semiconductor we add trivalent impurity.
When we add a trivalent impurity like aluminium boron etc, dopant atom will form covalent bond with neighbouring atom but since it has 3 valence electrons and the intrinsic semiconductor material has 4 valence electrons. So, there will be a vacancy or a hole. To complete the bonding an extra electron will be needed and this will come from the neighbourhood again creating a hole in its own site.
Since, we have trivalent impurity we have a large number of holes. The hole is the majority charge carrier for p-type semiconductor.
The number of electrons in a p-type semiconductor is very small compared to the no of holes. Electrons are the minority charge carriers.
So, in a p-type semiconductor both the holes and electrons are charge carriers but the number of holes is very large compared to the number of electrons.
So, the charge carriers in a p-type semiconductor are holes in large no and electrons in smaller numbers.
The correct option is (c).

Additional information:
Conductivity of a material can be defined as the extent to which the material can conduct electricity. It is equal to the reciprocal of conductance.
For n-type semiconductor electrons are the majority charge carriers and holes are the minority charge carriers.

Note: For an intrinsic semiconductor the number of electrons and number of holes are equal. But for an extrinsic semiconductor the number of carriers is different depending on the impurity added.
For intrinsic semiconductor ${{n}_{e}}={{n}_{h}}={{n}_{i}}$
For extrinsic semiconductor ${{n}_{e}}{{n}_{h}}={{n}_{i}}^{2}$ in thermal equilibrium.