Question
Which of the following semiconductor materials contains excess free electrons?
Answer Options
- A) N-type
- B) P-type
- C) Bipolar
- D) Insulated gate
Correct Answer: A
Explanation
A pure semiconductor material (like silicon) becomes electrically conductive when it is ‘doped’ with impurities. This doping process determines the type of charge carrier that dominates conduction. Semiconductors are classified as either N-type or P-type.
N-type semiconductor material is created by doping the pure material with pentavalent impurities (atoms with five valence electrons, such as phosphorus or arsenic). This process introduces extra valence electrons that are weakly bound to the crystal structure, resulting in excess free electrons available for conduction. In N-type material, electrons are the majority carriers.
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