Let's consider a PN junction between two semiconductor doped P and N. Let's concentrate on the N side for example. Due to Fick law, the electrons from the N side migrate to the P side.
What is the origin of these electrons that migrate : the N doped atoms or the non doped atoms ? Or both ? Is one source dominant ? If yes, which one, and why ?
Do all additive electrons of the N doped atoms migrate or only a subfraction ?
Do some electrons of non doped atoms migrate also ?