The detailed mechanism of internal electric field to prevent the multi-carrier diffusion of PN junction should be considered from two angles, one is the angle of non-electric field and the other is the angle of electric field.

Non-electric field angle:

Not because of the internal electric field, but because the diffusion is not caused by the initial electric field, but because of the diffusion formed by uneven concentration, and the result of diffusion is the pn junction formed in the middle neutralization.

With the continuous diffusion, the pn junction becomes thicker and thicker. The concentration difference of this pn junction is already zero, which will prevent the drift from going on. At first, it was thin, and the diffusion force was relatively large. Many carriers can be neutralized in the past, and the result is thicker and thicker. Finally, the diffusion force has no power to break through this wall and then reach a balance.

Electric field angle:

Generally, the formation of ions is caused by negative ions and positive ions formed by an atom because of gaining or losing electrons, and their structures are unstable. Positive ions are produced by atoms losing electrons due to external forces. The positive charge of a proton is greater than the number of electrons moving around it, so it has the ability to acquire electrons and stabilize its structure, that is, the positive and negative charges are equal.

Negative ions are the same, and one more electron makes you feel uncomfortable. So when these two ions meet, they will be neutralized.

Extended data

In the PN junction, it is assumed that the N-type material and the P-type material are physically separated, and the Fermi level in the N-type material is close to the bottom of the conduction band and the Fermi level in the P-type material is close to the top of the valence band, as shown in the right figure.

When the P-type material and the N-type material are connected together, the Fermi level must be constant in the thermal balance, otherwise, according to the modified ohm's law, the condition of constant Fermi level will be realized by the current transferring from the N-type side to the P-type side and holes in the opposite direction.

References:

Baidu encyclopedia-built-in electric field