FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsEasy
A technician wants to create N-type semiconductor material from pure silicon, which has 4 valence electrons per atom. Which doping element should be added to accomplish this?
- ASilver, which has 1 valence electron
- BPhosphorus, which has 5 valence electrons
- CBoron, which has 3 valence electrons
- DGermanium, which has 4 valence electrons
Show answer & explanationAnswer & explanation
Correct answer: B. Phosphorus, which has 5 valence electrons
N-type material is created by doping silicon with a pentavalent element such as phosphorus or arsenic, which contributes an extra free electron to the crystal lattice, creating excess negative charge carriers.
Why the other options are wrong
- A. Silver is a conductor, not a doping agent used to alter semiconductor crystal structure.
- C. Boron has only 3 valence electrons and creates P-type material by producing holes.
- D. Germanium is itself a semiconductor with 4 valence electrons and does not dope silicon into N-type.
N-Type Semiconductor Doping
N-type silicon is produced by adding a pentavalent (5 valence electron) impurity, which supplies extra free electrons as majority charge carriers.
- Pentavalent dopants: phosphorus, arsenic, antimony
- Extra electron becomes a free carrier
- N-type carriers are electrons (negative)
Memory trick: 'N for Negative, Need 5' - N-type needs 5-valence dopants for extra electrons.