A question from sample HSC paper (excel). (1 Viewer)

[-X-]

Doping of semiconductors with a group 3 element:
A. Results in conduction by electrons only.
B. Results in conduction by holes only.
C. Causes conductivity to increase.
D. Causes conductivity to decrease.

Ok the answer says that its C. Shouldnt the answer be "B"? Since a semi-conductor is already able to conduct so theres no need to increase its conductivity (why would they wana do that anyway?). Am right or am i missing something (usually the case )?


Thanks

 

[Rahul]

doping actually enhances the conductivity of a semiconductor.

hmmm...i would have also said B, at first.

but if you think about it, what conducts electricity? electrons, so you cant get "holes" conducting electricity. the holes are regions that get left behind when an electron moves to the positive terminal. so, choosing B woul be quite silly

therefore, C would be the 'best' answer

 

[Fosweb]

It cant be B, because whilst adding a group 3 element causes an increase in holes, this does not stop electrons flowing. So there can't be conduction by "holes ONLY"

The only option there that suits is C.

But Rahul, in terms of semiconductors, the holes also allow a flow of current, and thus conduct electricity.

 

[-X-]

Ok thanks a lot then, C it is.

 

[Dash]

Damit... everyone beat me to it

But just a side note for you -X- incase you didn't already know, semiconductors doped with a group IV element are obviously better conductors than those doped with group III elements

 

[Rahul]

Originally posted by Fosweb
But Rahul, in terms of semiconductors, the holes also allow a flow of current, and thus conduct electricity.

yes, i thought i said that

holes allow a conduction of electricty, but not only holes. you need electrons aswell.

 

[Ryan-91]

damit... Everyone beat me to it

but just a side note for you -x- incase you didn't already know, semiconductors doped with a group iv element are obviously better conductors than those doped with group iii elements :d

wrong!

 

[Aerath]

Damit... everyone beat me to it

But just a side note for you -X- incase you didn't already know, semiconductors doped with a group IV element are obviously better conductors than those doped with group III elements

I think you might mean Group V?

 

[boxhunter91]

This post was back in 2003.
And yes better semiconductors use electrons as the current carrier which are doped by Group V elements.
These are n-type semiconductors.