Semiconductor Electronics: Materials CLASS 12

A semiconductor is a material whose electrical conductivity is between that of a conductor and an insulator.

• Conductors (like copper) have high conductivity.

• Insulators (like rubber) have very low conductivity.

• Semiconductors can conduct electricity under some conditions, making them very useful in electronics.

Common Semiconductor Materials

1. Intrinsic Semiconductors (pure form)

   • Made of a single element like Silicon (Si) or Germanium (Ge).

   • At room temperature, only a few electrons can move and conduct electricity.

   • Conductivity is low but increases with temperature.

2. Extrinsic Semiconductors (doped with impurities)

   • Conductivity is increased by adding small amounts of other elements.

   • Two types:

     • n-type: Extra electrons (negative charge carriers) added.

     • p-type: "Holes" (missing electrons acting as positive charge carriers) added.

Why Semiconductors are Special

• Their conductivity can be controlled by:

  • Temperature

  • Light (photoelectric effect)

  • Doping with impurities

• This controllability makes them essential for diodes, transistors, and integrated circuits.

Applications of Semiconductor Materials

1. Diodes – allow current to flow in one direction.

2. Transistors – amplify current or act as switches.

3. Solar cells – convert light into electricity.

4. LEDs – light-emitting diodes for displays and lighting.

5. Microchips – form the heart of all computers and smartphones.

Key Points to Remember

• Intrinsic = pure, Extrinsic = doped.

• n-type = electron majority carriers, p-type = hole majority carriers.

• Semiconductors form the basis of modern electronics.

• They can act as both conductors and insulators depending on conditions.