In a PN diode, does current flow between the conductors attached to the P and N types valence bands as well as their conduction bands?

Question

Although I've seen the typical no-bias, reverse-bias and forward-bias band diagrams associated with the PN junction and seen the overlapping valence and conduction bands of a typical metallic conductor, I can't find any example that include all four sandwiched together (conductor-Ntype-Ptype-conductor).  I'm curious about the physics of electron flow between the conductors' bands and those of the doped semiconductors in between.  Does that flow include not only their conduction bands, but their valence bands as well?

Frederic · Answer

If there is no bias, then there is no current flowing in the conductors on the sides of the PN junction. In this case, there is only a drift and diffusion current in the space charge region that cancels each other.
If there is a bias, then there is a net current flowing through the whole structure. In the metallic conductors, the current is carried by the free electrons near the Fermi level. In the N-doped semiconductor, the current is mainly carried by the electrons in the conduction band. In the P-type semiconductor, the current is mainly carried by the holes in the valance band.

In a PN diode, does current flow between the conductors attached to the P and N types valence bands as well as their conduction bands?

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