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Is the depleted region made only from ions coming from the doping of the semiconductor, or also from the atoms that have not been doped ? Are there non ionized atoms in the depleted region ? Do all electrons diffuse or only some of them ? If only a fraction, why ?

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  • $\begingroup$ google "space charge region". $\endgroup$ – The Photon Sep 13 at 17:36
  • $\begingroup$ Is this meant as a follow up to your previous question? $\endgroup$ – The Photon Sep 13 at 17:38
  • $\begingroup$ If it were totally depleted the device would explode. $\endgroup$ – my2cts Sep 13 at 18:23
  • $\begingroup$ I googled space charge region, but it was not going in deep details as the ones that I asked. Yes, it is a follow up from the previous question.question raised by the other question. $\endgroup$ – Mathieu Krisztian Sep 13 at 18:39
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Is the depleted region made only from ions coming from the doping of the semiconductor, or also from the atoms that have not been doped ?

The depletion region is made up of the main semiconductor atoms with a (usually) very small fraction of dopant atoms.

The charge in the depletion region is from the ionized dopant atoms.

Are there non ionized atoms in the depleted region ?

Generally we assume all dopant sites will be ionized, whether in the depletion region or otherwise. This is because acceptor states will be well below the Fermi level, and donor states will be well above the Fermi level (when they're not, which happens with very heavy doping, we say the doping is degenerate).

Note: it may not be possible to define a Fermi level in the depletion region, nonetheless we can assume dopant sites are ionized.

Do all electrons diffuse or only some of them ?

In the depletion region, we don't find any significant number of free electrons. Any that are present will be swept out to the n-side of the junction.

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  • $\begingroup$ many thanks for your explanations. $\endgroup$ – Mathieu Krisztian Sep 13 at 18:39
  • $\begingroup$ For the OP, note that the 'small fraction' is on the order of 1 in a million (doping level of 5E16/cm2) $\endgroup$ – Jon Custer Sep 13 at 19:15

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