Talking about doped semiconductors:
Atoms outer shell extends and overlaps with another ones outer shell (the conduction band), right? So when electrical field is applied to a semiconductor bar (lets say n-type) electrons start to flow in the bar, and then what happens? I know that the electrons in the outer shell/conduction band contribute to electrical current density (usually marked as "J").
But my question is: How is it done? How the outer electrons contribute to electron flow when other electrons flow by or however it is done.