How Does Conductivity Increase in N-Type Semiconductors?

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Discussion Overview

The discussion centers on the increase of conductivity in n-type semiconductors, particularly examining the relationship between the number of free electrons and holes, and how this affects overall conductivity. It involves theoretical considerations and conceptual clarifications regarding charge carriers in semiconductors.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions how conductivity can increase in n-type semiconductors when the product of holes and electrons remains constant, suggesting that an increase in free electrons leads to a decrease in holes, potentially negating any increase in conductivity.
  • Another participant asserts that holes in the conduction band cannot produce a current, as they are not mobile, similar to electrons in the valence band.
  • A subsequent participant challenges the previous assertion by asking why the concept of 'hole current' exists if holes cannot contribute to current flow.
  • Another reply clarifies that hole current is associated with holes in the valence band, which corresponds to the movement of electrons in the conduction band.

Areas of Agreement / Disagreement

Participants express disagreement regarding the role of holes and their ability to contribute to current. There is no consensus on the implications of increasing free electrons on overall conductivity.

Contextual Notes

Participants have not resolved the assumptions regarding the mobility of charge carriers and the definitions of hole current versus electron current.

gracy
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How conductivity increases in n type semiconductor as ni^2 (formula nh multiplied by ne=ni^2 where nh=number of holes per unit volume and ne=number of free electrons per unit volume and ni=number of intrinsic charge carrier per unit volume remain constant?What is the use of increased number of electrons in conduction band as increasing number of electrons in conduction band decreases number of holes which were also capable of producing current i.e increasing conductivity.So overall no net increase in conductivity because as we are increasing number of electrons in conduction band at the same time we are loosing number of holes.please explain this.
 
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Holes in the conduction band cannot produce a current. There is nothing that could move. Same with electrons in the valence band - they are bound and cannot move.
 
mfb said:
Holes in the conduction band cannot produce a current. There is nothing that could move. Same with electrons in the valence band - they are bound and cannot move.
so why there is a concept called ' HOLE CURRENT'?
 
gracy said:
so why there is a concept called ' HOLE CURRENT'?
The hole current is caused by holes in the valence band (this corresponds to electrons in the conduction band).
 
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