Donor impurities create states near the conduction band while acceptors create states near the valence band. Below is a band diagram of PN junction operation in forward bias mode showing reducing depletion width. Both p and n junctions are doped at a 1e15/cm3 doping level, leading to built-in potential of ~0.59V. Reducing depletion width can be inferred from the shrinking charge profile, as fewer dopants are exposed with increasing forward bias. Image credit: courtesy of nanohub.org
