Electrical Engineering ⇒ Topic : N-type Semiconductors

N-type Semiconductors

If a pentavalent atom (having five electrons in the outermost orbit) like arsenic, antimony, or phosphorus is added in small proportion to germanium, it replaces an equal number of germanium atoms without changing the physical state of the conductor. Out of five electrons, four electrons enter in covalent bond and the fifth one is set free to move from one atom to the other. This impurity is called donor. It is possible to inject billions of electrons by adding a small amount of arsenic. Therefore, the conductivity increases enormously. Since majority carriers of   are electrons, such crystals are called N-type semiconductors