Question

Write the different methods of doping a semiconductor.

Answer 1

Hint: In this question we have been asked to write the different methods of doping a semiconductor. Therefore, before discussing the methods of doping a semiconductor, we shall discuss what is doping and why is there a need for doping. Later, we shall discuss the methods of doping a semiconductor. Doping is the process of adding impurities to a semiconductor.

Complete answer:
While producing a semiconductor, the process of intentionally adding impurities into an intrinsic semiconductor is known as doping a semiconductor. It is done in order to modulate the electrical, optical and structural properties of a semiconductor. The conductivity of semiconductors is also controlled by controlling the process of doping.
The impurities added to intrinsic semiconductors are known as dopants. We know that diffusion is the net transport of molecules from higher concentration to lower concentration. In a silicon lattice the dopants can be added in three ways.
1) empty space diffusion: In this method the dopants fill the empty places in crystal lattices. 2) inner lattice diffusion: In this method the atoms of dopants move in between the lattice of semiconductor material.
3) changing of places: This method is used when impurity atoms are present in the lattice. These atoms change places with crystal lattice.
The adding of dopants can be done by one of the three following ways:
1) When the silicon is in molten state the dopant atoms can be added to it.
2) When the ions of impurity atoms are bombarded onto the intrinsic semiconductor, the dopants get added in the new under production semiconductor.
3) The impurity atoms can be added to the semiconductor if they are heated in a semiconductor crystal container.

Note:
When the trivalent impurity is added to the intrinsic semiconductor, the semiconductor is said to be p-type semiconductor. A large number of holes, which are the charge carriers are then generated in p-type semiconductor. When a semiconductor is doped with pentavalent impurities, the semiconductor is called n-type semiconductors. The electrons are the charge carriers in this semiconductor.