N-type of semiconductor

[gracy]

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.

 

[mfb]

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.

 

[gracy]

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'?

 

[Vagn]

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).