1. The formation that PN writtens guarantee

(1) when be united in wedlock together with N semiconductor when P semiconductor, because hand in an interface to be in existence to carry,flow child pH indicator difference, such electrons and cavity want to diffuse from the place with the ground direction low concentration with high concentration. But, electron and cavity are electrified, what the result that they diffuse makes P area and N area Central Plains come is electrically neutral the condition was destroyed. P area a side leaves the anion that cannot move because of losing hole, n area a side leaves what cannot move because of losing an electron ionic. The electrified particle that these cannot move calls space charge normally, they are centered around P area and face of N area have a common boundary, formed a very small space charge division, this is the PN form that we say.

Graph (1) chroma appoint carries stream child produce enlarge to come loose motion

(2) inside this area, majority carries stream child already diffused the other side is compound dropped, perhaps say to used up almost to use up, accordingly, space charge area calls depletion layer again.

(3) P area a side presents negative electric charge, n area a side presents positive electrical charge, because area of this space charge appeared,direction points to the electric field of P area by N area, because this electric field is to carry,flow child diffuse motion forms, extra voltage does not form, reason is called inside electric field.


Graph (2) inside electric field is formed

(4) inside electric field is by how child diffuse motion causes, companion builds as it will bring two kinds of influences: It is inside block up of electric field general is much child diffuse, 2 be P area and N area is little child once * is close,PN writtens guarantee, the other side reachs adrift below the action of electric field inside, make narrow of space charge area.

(5) accordingly, diffuse motion makes broaden of space charge area, electric field increases inside, be helpful for little child drift and go against much child diffuse; And drift motion makes narrow of space charge area, inside electric field is abate, be helpful for much child diffuse and go against little child drift.
Should diffuse to move and move adrift when achieving dynamic balance, face of have a common boundary forms stable space charge division, namely PN knot is in trends to balance S.

Previous12 Next