# Variation of Potential outside a PN junction

Tags:
1. Oct 21, 2015

### Amal Thejus

1. The problem statement, all variables and given/known data
1. We are considering a step junction at equilibrium(no external voltage applied).

2. The potential variation is shown as negative potential at P region(which is shown as constant) and increasing through the transient region to become positive in the n region.

2. Relevant equations
Potential V=Q/4ΠΣ

3. The attempt at a solution
1. As per the equation for potential, the value of potential at the P region should be positive(since Q=positive here) and shown at a higher level than the negative potential in the N region(since Q=negative here).

2.Also the positive potential at P region should drop to a negative value in the transition region next to it(because of the presence of electrons there at equilibrium) and slowly increase to become positive potential as the transient region changes from negative to positive. As the positive region comes to an end the graph should again become negative due to the electrons in the N region.

#### Attached Files:

• ###### IMG_20151021_165536.jpg
File size:
36.4 KB
Views:
47
2. Oct 21, 2015

### ehild

A p or n-type semiconductor is neutral. When an n-type piece is in contact with a p-type piece, some of the free carriers migrate to the other side, electrons from the n-type part and holes form the p-type part. These holes make the region near the pn junction positive, and the electron, having diffused to the p-type side, make a negative region near the junction.

3. Oct 21, 2015

### Amal Thejus

Thank you so much. That was kind of a stupid question right. I can't believe I missed the material being neutral. Thanks again.