The formation of PN Junction

P-Type Semiconductors

A P-type semiconductor is formed by adding 3 valence elements such as boron to a pure silicon crystal to replace the position of the silicon atom in the lattice. In the P-type semiconductor, the hole is multi-word, the free electron is the small son, mainly by the hole conduction. The more impurities are added, the greater the concentration of the holes, and the stronger the conductivity.

N-Type semiconductors

N-Type semiconductors are formed when a pure silicon crystal is doped with 5 valence elements such as phosphorus to replace the position of the silicon atoms in the lattice. In n-type semiconductors, the concentration of free electrons is greater than the concentration of holes, so free electrons are multi-sons and holes are few. Such as:

The formation of PN Junction

When the N-type and P-type semiconductors are made together, there must be a diffusion movement. The free electrons in n region spread to the P zone, and the hole in P region spread to n region. Due to the diffusion of free electrons and holes in the P-zone compound, the diffusion to the N-off hole and free electrons compound, so in the vicinity of the junction of the concentration of the sub-area, the P-zone negative ion zone, n zone, they can not move. Called the space charge Zone, also known as depletion layer, thus forming an internal electric field. With the spread movement, the space charge area is wide, the internal electric field is enhanced, and its direction is n pointing p, which stops the spreading movement. Such as:

The formation of PN Junction