What is semiconductor ? Describe the two main types of semiconductors and contrast their conduction mechanism.
What is semiconductor ? Describe the two main types of semiconductors and contrast their conduction mechanism.
These solids have conductives in the intermediate range from 10−6 to 104ohm−1m−1. As there is rise in the temperature, conductivity also increases because electrons from the valence band jump to conduction band.
Types of semiconductors
(a) n - type semiconductor when silicon or germanium crystal is doped with group 15 element like P or As, the dopant atom forms four covalent bonds like a Si or Ge atom but the fifth electron no used in bonding, becomes delocalised and contribute its share towards electrical conduction. Thus, silicon or germanium doped with P or As is called n-type semiconductor (negative - type).
(b) p - type semiconductor When silicon or germanium is doped with group 13 element like B or Al. The dopant atom forms three covalent bond like a B or Al atom, but at the place of fourth electron a hole is created. Here, this hole moves through the crystal like a positive charge giving rise to electrical conductivity.
Thus, Si or Ge doped with B or Al is called p-type of semiconductor, (p stands for positive hole) since, it is the positive hole that is responsible for conduction.
These solids have conductives in the intermediate range from 10−6 to 104ohm−1m−1. As there is rise in the temperature, conductivity also increases because electrons from the valence band jump to conduction band.
Types of semiconductors
(a) n - type semiconductor when silicon or germanium crystal is doped with group 15 element like P or As, the dopant atom forms four covalent bonds like a Si or Ge atom but the fifth electron no used in bonding, becomes delocalised and contribute its share towards electrical conduction. Thus, silicon or germanium doped with P or As is called n-type semiconductor (negative - type).
(b) p - type semiconductor When silicon or germanium is doped with group 13 element like B or Al. The dopant atom forms three covalent bond like a B or Al atom, but at the place of fourth electron a hole is created. Here, this hole moves through the crystal like a positive charge giving rise to electrical conductivity.
Thus, Si or Ge doped with B or Al is called p-type of semiconductor, (p stands for positive hole) since, it is the positive hole that is responsible for conduction.
