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In order for our silicon crystal to conduct electricity, we need to introduce an impurity atom such as Arsenic, Antimony or Phosphorus into the crystalline structure. These atoms have five outer electrons in their outermost co-valent bond to share with other atoms and are commonly called "Pentavalent" impurities. This allows four of the five electrons to bond with its neighbouring silicon atoms leaving one "free electron" to move about when an electrical voltage is applied (electron flow). As each impurity atom "donates" one electron, pentavalent atoms are generally known as "Donors". Antimony (symbol Sb) is frequently used as a pentavalent additive as it has 51 electrons arranged in 5 shells around the nucleus. The resulting semiconductor material has an excess of current-carrying electrons, each with a negative charge, and is therefore referred to as "N-type" material with the electrons called "Majority Carriers" and the resultant holes "Minority Carriers".
N-Type Extrinsic semiconductor - Video:
Semiconductors: 3D Animation Video: