To a germanium crystal equal number of aluminium and indium atoms are added. Then,
To a germanium crystal equal number of aluminium and indium atoms are added. Then, Correct Answer it becomes a p - type semiconductor
CONCEPT:
- Doping: The process of adding impurities to a pure (intrinsic) semiconductor is called doping.
- By doing this, the conductivity of the semiconductor is increased drastically even at room temperatures.
- It is needed because the conductivity of a pure semiconductor like silicon or germanium is very low at room temperatures.
- Doping leads to the formation of extrinsic semiconductors which are of two types: n-type and p-type.
- N-type semiconductors have impurities of elements from Group 5 of the periodic table, hence electrons are the majority charge carriers.
- P-type semiconductors have impurities of elements from Group 3 of the periodic table, hence holes are the majority charge carriers.
EXPLANATION:
- When a trivalent impurity is doped in an intrinsic semiconductor (silicon) then we got a P-type semiconductor. For example: gallium, indium. Therefore option 3 is correct.
- In a p-type semiconductor, holes are generated because the trivalent impurity atom has one less electron than the surrounding silicon atom.
- Thus, leaving a vacancy in a covalent bond that acts as a hole.
- The presence of a hole does not make the semiconductor material positively charge because in an impurity atom, no. of electron and proton is equal before and after the doping, and the same applies for the silicon atom.
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Feb 20, 2025