N-Type Semiconductors are created when doping a semiconductor with impurities that adds extra valence electrons to the outermost shell to share free electrons with neighboring atoms. Phosphorous, arsenic and antimony are examples of atoms with five valence electrons, also known as pentavalent impurities, adding an extra electron for each doped atom. This does not mean however that an N-type semiconductor is negatively changed, because there will exist a balancing positive charge in the nucleus of the doped atom. An N-type semiconductor is a better conductor than intrinsic semiconductor materials.
P-Type Semiconductors are formed by adding group 3 elements, known as trivalent impurity atoms such as boron, aluminum and indium to the semiconductor structure. These atoms have only three electrons in the outermost shell, producing an extra electron hole, which attracts neighboring electrons.
To recap, N-type semiconductors:
- possess pentavalent elements as impurity atoms to add a donor electron to the material.
- do not have a negative charge since atom nucleus charge offsets added electrons, meaning they are electrically neutral.
- possess trivalent impurity elements as impurity atoms to add an electron hole.
- are also electrically neutral.