PN junctions and diodes
In a PN junction where the p side is far more heavily doped than the n side (a p+n junction), how does the depletion layer spread?
- AIt spreads mostly into the lightly doped n side
- BIt spreads mostly into the heavily doped p side
- CIt always spreads equally into both sides
Show answer and explanation
Answer: A. It spreads mostly into the lightly doped n side
The amount of ionized impurity charge is equal on both sides of the depletion layer. The lightly doped side must be depleted over a wider region to provide the same charge, so the depletion layer spreads mainly into the lightly doped side. This is a basic idea in designing breakdown voltage.