p-type Semiconductor

A p-type semiconductor is a group IV intrinsic semiconductor such as silicon (Si) doped with group III boron (B) or indium (In) as an impurity.

Group IV elements are tetravalent elements with four valence electrons, while group III elements are trivalent elements with three valence electrons. A single crystal made only of tetravalent elements such as Si is an intrinsic semiconductor in which all bonds are connected to other elements by covalent bonds. When a small amount of boron is added to this single crystal (diffusion/doping), an electron becomes insufficient at one of the bonds between silicon and boron, creating a hole where an electron is missing. This hole is called a hole. When a voltage is applied in this state, a nearby electron moves to the hole, so the place where the electron was becomes a new hole, and it appears that the holes move one after another to the negative pole.

In a p-type semiconductor, the particles (carriers) that carry the charge are holes. Since holes are the parts where there is a shortage of electrons, they have a positive charge. For this reason, they are called p-type.