The wiki describes it as- "After joining p-type and n-type semiconductors, electrons from the n region near the p–n interface tend to diffuse into the p region leaving behind positively charged ions in the n region and being recombined with holes, forming negatively charged ions in the p region. Likewise, holes from the p-type region near the p–n interface begin to diffuse into the n-type region, leaving behind negatively charged ions in the p region and recombining with electrons, forming positive ions in the n region[further explanation needed]. The regions near the p–n interface lose their neutrality and most of their mobile carriers, forming the space charge region "

My doubt is if for eg we take N type interface then electrons are getting diffused from it to P interface and if these electrons are combining with holes in P interface,shouldn't the electrons and holes neutralise each other and hence no charge is there on P interface or is it talking about the combined process in which though electrons are getting neutralised at P interface,the holes are also getting transported resulting in net negative charge.....assuming my neutralisation assumption is correct?

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    $\begingroup$ "shouldn't the electrons and holes neutralise each other and hence no charge is there on P interface" - The P type material is electrically neutral before the electrons diffuse to the P side so when an electron diffuses to the P side, the P side becomes more negatively charged. Recombination with a hole there does not change this fact. Is this what you're asking about? $\endgroup$ – Alfred Centauri Dec 19 '17 at 16:05
  • $\begingroup$ @Alfred Centauri But imagine.....an extra electrons comes at P and holes get transported from P,can't they happen simultaneously at equal rates so as to maintain electrical neurality at P? $\endgroup$ – user176273 Dec 19 '17 at 16:11
  • $\begingroup$ harambe, when a hole leaves P, P becomes more negatively charged just as when an electron enters P so how could electric neutrality be maintained by making their rates equal? $\endgroup$ – Alfred Centauri Dec 19 '17 at 16:37
  • $\begingroup$ @Alfred Centauri I get it now...so the lectric charge at P is due to both transportation of holes and electrons,am i right? $\endgroup$ – user176273 Dec 19 '17 at 16:39
  • $\begingroup$ Basically, in a semiconductor it is always a combination of electrons and holes that need to be considered... $\endgroup$ – Jon Custer Dec 19 '17 at 17:31

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