Electrical Engineering XYZ MCQs
What will be the result if pentavalent impurity is added to pure germanium or silicon:
- P-type semiconductor
- N-type semiconductor
- Intrinsic semiconductor
- None of the above
Correct answer: 2. N-type semiconductor
Explanation: When a pentavalent impurity, such as phosphorus or arsenic, is added to pure germanium or silicon, it introduces extra electrons into the crystal lattice. These impurity atoms have five valence electrons, with four of them forming covalent bonds with the neighboring atoms in the crystal lattice, leaving one extra electron. This extra electron is relatively loosely bound and can move freely in the crystal lattice, contributing to the conductivity of the material.
This type of doping creates an excess of negative charge carriers (electrons) in the semiconductor, thereby making it an N-type semiconductor. In N-type semiconductors, electrons are the majority charge carriers, and their mobility determines the conductivity of the material.