==Forward bias==
In forward bias, the p-type is connected with the positive terminal and the n-type is connected with the negative terminal.[[File:PN band.gif|thumb|750px|center|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 ~0.59 V. Reducing depletion width can be inferred from the shrinking charge profile, as fewer dopants are exposed with increasing forward bias.]]
With a battery connected this way, the [[Electron hole|holes]] in the P-type region and the [[electrons]] in the N-type region are pushed toward the junction. This reduces the [[depletion width|width]] of the [[depletion zone]]. The positive potential applied to the P-type material repels the holes, while the negative potential applied to the N-type material repels the electrons. As electrons and holes are pushed toward the junction, the distance between them decreases. This lowers the barrier in [[electrical potential|potential]]. With increasing forward-bias voltage, the depletion zone eventually becomes thin enough that the zone's electric field cannot counteract charge carrier motion across the p–n junction, as a consequence reducing electrical resistance. The electrons that cross the p–n junction into the P-type material (or holes that cross into the N-type material) will diffuse in the near-neutral region. Therefore, the amount of minority diffusion in the near-neutral zones determines the amount of current that may flow through the diode.
Only [[majority carriers]] (electrons in N-type material or holes in P-type) can flow through a semiconductor for a macroscopic length. With this in mind, consider the flow of electrons across the junction. The forward bias causes a force on the electrons pushing them from the N side toward the P side. With forward bias, the depletion region is narrow enough that electrons can cross the junction and ''inject'' into the P-type material. However, they do not continue to flow through the P-type material indefinitely, because it is energetically favorable for them to recombine with holes. The average length an electron travels through the P-type material before recombining is called the ''diffusion length'', and it is typically on the order of [[micrometers]].{{cite book |title=Solid State Physics |last=Hook |first=J. R. |author2=H. E. Hall |year=2001 |publisher=John Wiley & Sons |isbn=0-471-92805-4 }}
Although the electrons penetrate only a short distance into the P-type material, the electric current continues uninterrupted, because holes (the majority carriers) begin to flow in the opposite direction. The total current (the sum of the electron and hole currents) is constant in space, because any variation would cause charge buildup over time (this is [[Kirchhoff's circuit laws#Kirchhoff's current law (KCL)|Kirchhoff's current law]]). The flow of holes from the P-type region into the N-type region is exactly analogous to the flow of electrons from N to P (electrons and holes swap roles and the signs of all currents and voltages are reversed).
Therefore, the macroscopic picture of the current flow through the diode involves electrons flowing through the N-type region toward the junction, holes flowing through the P-type region in the opposite direction toward the junction, and the two species of carriers constantly recombining in the vicinity of the junction. The electrons and holes travel in opposite directions, but they also have opposite charges, so the overall current is in the same direction on both sides of the diode, as required.
The [[Diode#Shockley diode equation|Shockley diode equation]] models the forward-bias operational characteristics of a p–n junction outside the avalanche (reverse-biased conducting) region.