Explain with diagram, how current flows due to electron and hole in pure semiconductor.

Explanation

The semiconductor has the unique properties which the hole also moves in addition to the electrons.

Suppose there is a hole at site 1 as shown in figure (b).
An electron from the covalent bond at site 2 may jump to the vacant site (hole).
Thus, after such a jump, the hole is at site 2 and the site 1 has now an electron.
Hence, the hole and the electrons move in opposite direction. Here due to heat the electron released from the covalent bond do not involved in this process.
The free electron moves completely independently as conduction electron and gives rise to an electron current, `I_(e )` under an applied electric field.
Hole is in a covalent bond. It move from high electric potential to low electric potential under the influence of external electric field applied when a hole is formed in a crystal. It is a convenient way of displaying and motion of hole created hole current. In thus, we get two type of currents in semiconductors.
(1) Due to motion of free electron.
(2) Due to motion of formation of hole and instantaneous jumping electron in other hole.
Hence in semiconductor, the total current I is the sum of the electron current `(I_(e ))` and the hole current `(I_(h))`.
`therefore I=I_(e )+I_(h)`