What is Intrinsic Semiconductor ?

Intrinsic semiconductors are semiconductors that are pure i.e. it does not contain any impurity. Since it does not contain any impurity, the number of free electrons and the number of holes are equal. It is also known as an i-type semiconductor. The number of free electrons and the number of holes depends on the property of the material and does not depend on the doping.

For intrinsic semiconductors

 n = p

where, n=number of electron, m=number of holes.

On the basis of electrical conductivity, materials are classified as:

1. Conductors: Good conductors of electricity
2. Insulators: Bad conductors of electricity
3. Semiconductors: These materials have conductivity levels between those of conductors and insulators.

On the basis of the amount of doping, semiconductors are Classified as:

1. Intrinsic Semiconductors
2. Extrinsic Semiconductors

Example of Intrinsic Semiconductors :

Silicon and germanium are the best examples of Intrinsic semiconductors.

Free Electrons and Holes

Electrons that are available, for the flow of the current, above 0 Kelvin or above -273 degree Celcius is known as free electrons. Above 0 kelvin, these electrons gain energy and cross the energy band gap, leaving behind an empty space. This empty space is known as a hole. Holes are treated as +ve charges because there is a deficiency of -ve charge at that place.

How do Intrinsic Semiconductors Work?

To understand the working mechanism of intrinsic semiconductors, we need to know the electronic configuration of their atoms.

The electronic configuration of silicon and germanium are:

1. Silicon –> 1s²  2s² 2p⁶  3s²  3p²

2. Germanium –> 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p²

We can clearly see that the outermost shell is having 4 electrons. At 0 Kelvin, the semiconductor behaves like a pure insulator. Now, with the increase in the temperature, electrons gain enough energy to free from its shell and leave behind an empty place known as a hole. Thus, a free electron is produced along with a hole.This is the reason for the equal number of electrons and holes in intrinsic semiconductors.

Key Points of Intrinsic Semiconductors

1. Intrinsic semiconductors uses electrons and holes for conduction at room temperature.
2. At 0 Kelvin (absolute temperature), intrinsic semiconductors behave like pure insulators.
3. When an intrinsic semiconductor is doped with an impurity, it gets converted into an extrinsic semiconductor.