Semiconductors valence and energy bands

[gracy]

valence band and conduction band overlap in conductors but not in semiconductors and insulators why?t

 

[DrDu]

Well, full bands give no contribution to conductivity, so if all bands are either full or empty, you get an insulator. To get a metal, (i.e. non-zero conductivity) some band has to be occupied only partially. Overlap of valence and conduction band is but one possibility. In this case, both valence and conduction band will contribute to conductivity. The other possibility is that the conduction band is not completely filled, without this being due to an overlap with the valence band.

 

[gracy]

Well, full bands give no contribution to conductivity, so if all bands are either full or empty, you get an insulator. To get a metal, (i.e. non-zero conductivity) some band has to be occupied only partially. Overlap of valence and conduction band is but one possibility. In this case, both valence and conduction band will contribute to conductivity. The other possibility is that the conduction band is not completely filled, without this being due to an overlap with the valence band.

ok i have one more question
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?

 

[DrDu]

Please don't use bold fond for entire text. This is considered "shouting".
Maybe you can tell us something about the background of your question and about your educational background?

 

[gracy]

actually yesterday my keyboard was not working .i had asked the same question on yahoo but didn't get the answer ,as my keyboard was not working i couldn't type so i copy pasted the question from my yahoo account to here .you must be knowing on yahoo question are wrriten in bold letters .but i am really sorry for that.
thanks

 

[DrDu]

That's no problem.
I would recommend you to read some introductory text on band structures first. To recommend you some text it would be nice to know something about your educational background.