Semiconductors - Multiple choice (1 Viewer)

[middlemarch]

This question is from the cssa '01 trial

If an atom from group 3 is used as the impurity in a semiconductor, conductivity increases because of an:
a) increase in no. of free electrons
b) alteration to the metal lattice of the semiconductor.
c) increase in no. of +ve holes in crystal lattice
d) increase in energy of the conduction band

The answer is supposed to be a).
Can anybody explain why it's not C?

Thx
Middle

 

[LostAuzzie]

I agree with you on that one it should be C
Group 3, 3 electrons
Bonded in with semi-conductor, 4 spaces
Thus one space left over (positive hole)

The only thing I can possibly think of is that its referring to electrons being attracted to the holes.

 

[middlemarch]

Yeah...thought so.
There must be a misprint then.
Thanks for confirming