What is an intrinsic semiconductor? Give two examples.

Hint: In this question we will study intrinsic semiconductor and its example. Intrinsic semiconductor is a pure semiconductor in which the number of holes is equal to the number of electrons. No impurity of other atoms exists in an intrinsic semiconductor.

Complete answer:
Let’s discuss in deep,
An intrinsic semiconductor is an inborn, naturally occurring, pure, or basic semiconductor. The best examples of intrinsic semiconductors are crystals of Pure Silicon and Pure Germanium.
We know that Si and Ge have 4 valence electrons and these two elements possess properties like Carbon because they are tetravalent.
All four electrons of Si and Ge crystals are involved in covalent bonding and no electron sets free; this is the property of catenation that we can see in Carbon also.
Concept of Hole and Electron:
So far, we understood that by applying an electric field to the semiconductor, the electrons start leaving the conduction band and fall.
Now, electrons start falling and they unite with vacancies or holes, so the process of the meeting of electrons with holes is called recombination.
Now, as the temperature rises, more electrons migrate to the conduction band and thus supersedes the recombination process. At this moment, the semiconductor conductivity increases with the temperature rise.

Note:
A number of thermally generated electrons equals the number of holes generated.
The intrinsic concentration is the intrinsic charge carrier density of the semiconductor, and it is symbolized as ${n_i}$ . The ${n_i}$ value for $Si$ and $Ge$ are as follows:
$
  Si = {n_i} = 1.5 \times {10^6}{m^{ - 3}} \\
  Ge = {n_i} = 2.4 \times {10^{19}}{m^{ - 3}} \\
 $