about p type semiconductor and n type semiconductor
Answers
The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors.
Pentavalent impurities
(5 valence electrons) produce n-type semiconductors by contributing extra electrons.
Trivalent impurities
(3 valence electrons) produce p-type semiconductors by producing a "hole" or electron deficiency.
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Question = What is a n-type semiconductor and p-type semiconductor ?
ANSWER :- N- TYPE SEMICONDUCTOR ==>When silicon or germanium crystal is doped with a GROUP - 5 element like P or As the dopant atom forms 4 covalent bonds like a Si or Ge atom but the 5th electron, not used in bonding, becomes delocalised and contributes its share towards electrical conduction. Thus, silicon or germanium doped with P or As is called N-TYPE SEMICONDUCTOR, therefore n indicates negative charge of electron since it is the electron that conducts electricity.
P - TYPE SEMICONDUCTOR ==> When silicon or germanium is doped with a group 13 element like B or Al, the dopant atom forms 3 covalent bonds , but at the place of fourth electron a hole is created. 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 semiconductor ( P stands for +ve hole ), since it is the +ve hole that is responsible for conduction.