Doping in semicondctors (n type)

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Summary:

why do group 15 share the same conduction band as the silicon atoms.

Main Question or Discussion Point

Summary: why do group 15 share the same conduction band as the silicon atoms.

In a n type extrinsic semiconductors the atoms of silicon are doped with the atoms of a gr15 element to increase the number of valance electrons in the semiconductor. But the reason given to me by my teacher and what I've seen online is that the valance band of the gr15 elements is closer to the valance band of the silicon atoms, making it easier for the electrons form the valance band of the gr15 atom to jump to the conduction band with minimal amount of energy. But why is it that the gr 15 element used has the same energy level for the conduction band as the silicon atoms.
Is it possible that the presence of the silicon atoms has an effect on the conduction band of the element.
 

Answers and Replies

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The conduction band is always the result of the overall crystal, not individual atoms. The energy levels of an element as pure crystal are very different from the behavior of atoms of that element when in another element.
Summary: why do group 15 share the same conduction band as the silicon atoms.

But the reason given to me by my teacher and what I've seen online is that the valance band of the gr15 elements is closer to the valance band of the silicon atoms, making it easier for the electrons form the valance band of the gr15 atom to jump to the conduction band with minimal amount of energy.
You mean "closer to the conduction band"? Otherwise the sentence is inconsistent.

(valence with e, by the way)
 
Mister T
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In a n type extrinsic semiconductors the atoms of silicon are doped with the atoms of a gr15 element to increase the number of valance electrons in the semiconductor.
That's what makes it n type!

But the reason given to me by my teacher and what I've seen online is that the valance band of the gr15 elements is closer to the valance band of the silicon atoms, making it easier for the electrons form the valance band of the gr15 atom to jump to the conduction band with minimal amount of energy.
Both explanations seem correct. You have more electrons and those electrons don't need a lot of energy to make it up to the valence band. Both factors are going to contribute to a larger number of electrons in the conduction band.
 

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