Why Do Electrons Jump into the Conduction Band in Semiconductors?

[gracy]

What exactly is conduction band?electrons from valence band jump into conduction band where they exactly go ,do they go to higher shell or subshell or orbital or stays in same place with more kinetic energy?

 

[Drakkith]

What exactly is conduction band?electrons from valence band jump into conduction band where they exactly go ,do they go to higher shell or subshell or orbital or stays in same place with more kinetic energy?

The conduction band is a range of energy levels where electrons are free to roam about between multiple atoms. Electrons jumping from the valence band into the conduction band are in a higher energy orbital than before.

 

[gracy]

In conductors valence band and conduction band overlap why?i mean does it mean that in conductors electrons gain more energy than semiconductors and insulators on giving same amount of energy from external source.
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[freude3]

Sometimes, depending on the background knowledge, it is useful to think in terms of the molecular orbital theory. In this case, the conduction band can be thought as a bunch of LUMO orbitals, while the valence band is a bunch of HOMO orbitals at zero Kelvins.

 

[mfb]

In conductors valence band and conduction band overlap why?

By definition of conductors.
How much do you know about Brillouin zones? They depend on the crystal structure and allow to estimate the energy ranges of the different bands. The details of the crystal structure then determine if there is overlap or not.

 

[Drakkith]

In conductors valence band and conduction band overlap why?i mean does it mean that in conductors electrons gain more energy than semiconductors and insulators on giving same amount of energy from external source.
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No, it just means that the electrons in the valence band can already roam about the material without having to gain any extra energy.

 

[ZapperZ]

In conductors valence band and conduction band overlap why?i mean does it mean that in conductors electrons gain more energy than semiconductors and insulators on giving same amount of energy from external source.
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There is something here that you need to understand. When atoms are group together to form a solid, in many of their properties, they lose their individual behavior! The "atomic orbitals", at least at the low-lying energies, are now governed by a more collective properties. That is why there is a difference between the study of atomic/molecular physics, and solid state physics.

One of the examples where atoms lose their individuality is the formation of these so-called "bands", where in practice, these are a continuous range of allowed energy state. These are not found in isolated, individual atoms. So already the behavior of a solid within such an energy range is very different than the behavior of the individual atoms that make up that solid.

Zz.