Electron Band ( Foundation )

  

1. Electron band / band structure of a solid describes the ranges of energy an electron is "forbidden" or "allowed" to have

2. In Electron band,  the valence band is the highest range of electron energies.

3. But,the conduction band is the range of electron energies higher than that of the valence band,which it is sufficient to free an electron from binding with its individual atom and allow it to move freely within the atomic lattice of the material.)

4.  Any solid has a large number of bands.

5. In theory, a solid can have definitely many bands (just as an atom has infinitely many energy levels)

6. The lowermost, most fully occupied band in an insulator or semiconductor, is called the valence band by analogy with the valence electrons of individual atoms.

7. The uppermost, almost unoccupied band is called the conduction band because only when electrons are excited to the conduction band can current flow in these materials.

8. The difference between insulators and semiconductors is only that the “forbidden” ¹ between the valence band and conduction band is larger in an insulator.Meaning,conduction band² ( conduction band level is difficult to achieve,only those with very high energy can be there ) of insulator larger than valence band.

9. Hence,fewer electrons are found there and the electrical conductivity is lower.

Note :

1. This band gap is one of the most useful aspects of the band structure, as it strongly influences the electrical and optical properties of the material.

2. one of the main mechanisms for electrons to be excited to the conduction band is due to thermal energy, the conductivity of semiconductors is strongly dependent on the temperature of the material