nn junctions

**snoothie** · Nov6-09, 04:58 AM

Hi,

If we had two junctions one side with Nd=10¹⁶ & another side with Nd=10¹⁵ put together.

What happens in such a junction? Would we see electron diffusion from the high donor concentration side to the lower concentration side? What should the band diagram of the junction look like?

Does anyone have a link to any resources discussing about this online?
Thanks.

~~ernestpworrel~~ · Nov9-09, 01:27 AM

If you have an nn junction, all you have is a big lump of n-type material.

**berkeman** · Nov9-09, 01:54 AM

Originally Posted by snoothie

Hi,

If we had two junctions one side with Nd=10¹⁶ & another side with Nd=10¹⁵ put together.

What happens in such a junction? Would we see electron diffusion from the high donor concentration side to the lower concentration side? What should the band diagram of the junction look like?

Does anyone have a link to any resources discussing about this online?
Thanks.

What do you think the band diagram would look like?

**snoothie** · Nov10-09, 09:31 AM

Originally Posted by berkeman

What do you think the band diagram would look like?

think there will be a slight band bending due to a efield between the nn junctions which is due to the difference in donor concentrations? (gradient of 10^16 - 10^15 / x0 - x1)? then due to the field there should be some drifting of electrons from the n junction with higher nd concentration to the n junction with lower nd concentration?

not sure if i'm on the right track...

**xhongyi** · Nov16-09, 09:21 PM

Originally Posted by snoothie

think there will be a slight band bending due to a efield between the nn junctions which is due to the difference in donor concentrations? (gradient of 10^16 - 10^15 / x0 - x1)? then due to the field there should be some drifting of electrons from the n junction with higher nd concentration to the n junction with lower nd concentration?

not sure if i'm on the right track...

No you are not.
This would be a Schottky diode. And there would be a electron sheet just at the metalergical junction. So the bend diagram would be discontinuous as it would both decrease on the left and right part of the juctions but on the left part it decreases rapidly while the right part decreases gently. As a result, the end point of the left part would be much lower than the start point of the right part.

Assume the right part got highly doped.