N-Type Semiconductor

n-type Semiconductor

  1. The n-type semiconductor can be produced by doped some pentavalent atoms into a semiconductor.
  2. Pentavalent atoms are atoms that have 5 electrons in the valence shell. Examples of pentavalent atoms include antimony and phosphorus.
  3. The figure above shows how the silicon crystal appears after doped with a phosphorous atom, which is pentavalent.
  4. We can see that, the pentavalent atom form 4 covalent bonds with the silicon atoms around. Since a pentavalent atom has 5 electrons, there is an extra electron left over and it is a free electron.
  5. Each pentavalent in the silicon crystal produces one free electron. Therefore, the pentavalent atom is called the donour.
  6. The more pentavalent impurity that is added, the more free electrons in the semiconductor, and hence the greater the conductivity of the semiconductor.
  7. Some holes will also be formed in the semiconductor when some electrons are promoted to shell with higher energy level.
  8. The free electrons outnumber the holes, hence they are called the majority carrier and the holes are called the minority carriers.
  9. Since the negative charge carrier (the electrons) outnumber the positive charge carrier (the holes), the semiconductor is called an n-type semiconductor, where the n stands for negative.