Question

Distinguish between p-type and n-type semiconductors.

Answer 1

Hint: n-type and p-type semiconductors are made by doping a semiconductor with pentavalent and tetravalent impurity atom respectively. In the case of a p-type semiconductor, the conduction occurs due to the creation of a hole created with the addition of a tetravalent impurity.

Complete step by step answer:
A semiconductor is a type of material that normally behaves as an insulator but when a certain condition is like temperature is increased they start behaving as a conductor. To increase a semiconductor’s conductivity, they are doped with certain impurities. The element to which impurity is added is known as a dopant.
Based on the impurity added to the dopant, the semiconductor is of p-type and n-type:
- When a tetravalent semiconductor $Si$ (or $Ge$) is doped with a trivalent impurity such as $B$, $Al$, $Ga$, etc. the type of semiconductor formed is a p-type semiconductor. Since the addition of a trivalent impurity creates a hole that can accept an electron from the neighboring bond hence a trivalent impurity atom is known as an acceptor.
- Similarly, when a tetravalent semiconductor is doped with a pentavalent impurity, the type of semiconductor formed is an n-type semiconductor. Since, In the case of a pentavalent impurity, the atom gives an extra electron for conduction therefore in this case the pentavalent impurity is a donor.

Note:
- The phenomenon of adding a small amount of impurity to a substance to increase its conductivity is known as doping.
- In a p-type semiconductor, holes are the majority charge carrier, and electrons are the minority charge carrier.
- In an n-type semiconductor, the majority charge carriers are electrons whereas the holes are only a minority charge carrier.
- In the case of an n-type semiconductor, the current starts flowing due to the presence of an extra electron due to the addition of a pentavalent impurity.