# Semiconductor - Hall Effect

1. Apr 14, 2010

### Master J

A question on semiconductors.

I need to determine the carrier concentration and type.

I have worked out the type but its the conc. that is getting me.

I have the conc., n, as:

n = wBJ / eV

w is the width of sample, B the mag. field, e is charge, and V the Hall voltage...these are all known EXCEPT J. Now the only other pieces of info I have are the sample dimensions and the battery voltage that supplies the current.

I cant for the life of me see where I find J. I just cant get it!

Any pointers in the right directions?

2. Apr 14, 2010

### thebigstar25

one way to start is by noting that J = I/(wt) , where t is the thickness of the sample ..

3. Apr 14, 2010

### Master J

Yes, but i do not know the current? It leaves me in the same boat...

4. Apr 14, 2010

### thebigstar25

okay .. what if you considered the relation v = IR >> I = v/R .. you can get it dont give up :)

5. Apr 14, 2010

### Master J

Dont have R tho... :p

i only have the info as stated in the question. Damn im confused!

6. Apr 14, 2010

### thebigstar25

COME ON!! .. just break things up >> I cant help you with this one, I will just give hints .. you said you want R , so can you find another relation from where you can get R from what you are given in the question (of course other than R=V/I) >>> there is one please try to make some efforts I know sometimes it is not easy but atleast try harder ..