BECE MODULE 3

• Conductor - These are substances through which electricity
• Semiconductor - It is a material that conducts current, but only partly
• shells- Electrons in an atom are organized in layers, it’s like the layers of an onion
• valence shell- outermost shell
• Examples of conductors copper and silver,have one electron in the valence shell
• current to flow- valence electrons travel, they create moving electric fields that push other electrons out of their way
• three important semiconductor materials

  Si(Silicon)

  Ge(Germanium)

  GaAs(GalliumArsenide)
• Semiconductor - is a material that has electrical conductivity to a degree between that of a metal and that of an insulator
• Types of Semiconductor

  intrinsic Semiconductors- pure form of Semiconductor

  Extrinsic Semiconductors- An impure Form of Semiconductor
• Doping- process of adding impurities
• Classification of Extrinsic Semiconductor

  N Type Semiconductor- small number of pentavalent impurities is added

  P Type Semiconductor- denoting one extra electron for conduction
• donor impurity(donors) - denoting one extra electron for conduction
• Acceptor Impurity(Acceptors) - accepts free electrons in the place of the hole,