When a small amount of trivalent impurity (such as boron, gallium, indium or aluminium) is added to a pure semiconductor crystal during crystal growth, the resulting crystal is called a P-type semiconductor.

When a small amount of pentavalent impurity (such as arsenic, antimony, bismuth or phosphrous) is added to a pure semiconductor crystal during crystal growth, the resulting crystal is called the N-type semiconductor.   _{Your Comment}