Energy band diagram of a typical p+n{\displaystyle p^{+}n} step p-n junction that shows electron energy versus position.  Ec{\displaystyle E_{c}} is the conduction band, Ef{\displaystyle E_{f}} is the device fermi energy level, Ei{\displaystyle E_{i}} is the intrinsic Fermi level of the undoped semiconductor, and Ev{\displaystyle E_{v}} is the valence band.
Originally uploaded to the English language Wikipedia
Matt Britt at English Wikipedia