It is possible to shift the balance of electrons and holes in a silicon crystal lattice by "doping" it with other atoms. Atoms with one more valence electron than silicon are used to produce "n-type" semiconductor material, which adds electrons to the conduction band and hence increases the number of electrons. Atoms with one less valence electron result in "p-type" material. In p-type material, the number of electrons trapped in bonds is higher, thus effectively increasing the number of holes. In doped material, there is always more of one type of carrier than the other and the type of carrier with the higher concentration is called a "majority carrier", while the lower concentration carrier is called a "minority carrier."
Schematic of a silicon crystal lattice doped with impurities to produce n-type and p-type semiconductor material.
The following table summarizes the properties of semiconductor types.
| P-type (positive) | N-type (negative) | |
|---|---|---|
| Dopant | Group III (E.g. Boron) | Group V (e.g. Phosphorous) |
| Bonds | Missing Electrons (Holes) | Excess Electrons |
| Majority Carriers | Holes | Electrons |
| Minority Carriers | Electrons | Holes |
The animations below represent p-type and n-type silicon. In a typical semiconductor there might be 1017cm-3 majority carriers and 106cm-3 minority carriers. Expressed in a different form, the ratio of minority to majority carriers is less than one person to the entire population of the planet. Minority carriers are created either thermally or by incident photons.
N-type semiconductor. These are called "n-type" since the majority carriers are Negatively charged electrons.
P-type semiconductor. These are called "p-type" since the majority carriers are Positively charged holes.