14/04/2021

Mobile Charge Carriers & Immobile Ions

 

P type semiconductor

  • The P type semiconductor material is formed by addition of acceptor type impurity atoms ( gallium, indium, aluminum, boron ) to pure silicon / germanium crystals. 
  • The number of holes added is equal to the number of boron atoms ( acceptor impurities ) because each atoms contribute one hole. 
  • When hole moves away from its parent atom, the remaining atoms become negative ion. 
  • This ion cannot take part in the conduction because it is fixed in the crystal structure of semiconductor.


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N type semiconductor

  • Similarly, the N type semiconductor is formed by addition of donor type impurity atoms ( Antimony, Phosphorus, Arsenic ) to pure silicon / germanium crystals. 
  • The number of free and mobile electrons are equal to the number of donor impurity atoms. 
  • When electron moves away from its parent atom, it leaves behind positive ion.


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