Question

When a hole is produced in p-type semiconductor, there is
A. extra electron in valence band
B. extra electron in conduction band
C. missing electron in valence band
D. missing electron in conduction band

Answer 1

Recall the basic concept of p-type semiconductor like its formation and transfer of electric current in it. Then go through the concept of generation of holes in the p-type semiconductor for the transfer of electric current in it. Hence, determine the correct option from the given options.

Complete answer:
The semiconductor formed by addition of trivalent impurity in them is known as p-type semiconductor. The pure semiconductor has four electrons in its valence shell and trivalent impurity has three valence electrons.

When a trivalent impurity is added to a pure semiconductor like silicon or germanium, the three valence electrons in the pure semiconductor form a covalent bond with the three valence electrons in the trivalent impurity like gallium or indium. But there is one electron in atoms of pure semiconductor which do not have an electron to pair and form a covalent bond.

This space for an electron which is unoccupied to deficiency of electron is known as hole.These holes are the charge carriers in the p-type semiconductor. The electric current is carried by the p-type semiconductor by the transfer of holes with the adjacent atoms.

An electron from the valence shell of the adjacent atom jumps into the unoccupied place and forms a covalent bond. Meanwhile the electron donating atom has an unoccupied space. This space is then filled by the valence electron in neighboring atoms creating a hole in that atom. In such a way, there is transfer of electric current in the p-type semiconductor by the transfer of hole or transfer of electrons from valence shell of neighboring atom. Therefore, when there is a hole in a p-type semiconductor, there is a missing electron in the valence band.

Hence, the correct option is C.

Note: The students should be careful while giving the information about the generation of holes in the p-type semiconductor. If one gets confused between the p and n-type semiconductor then the steps in formation of holes will be incorrect and one will end with a wrong concept related with semiconductors.