Semiconductor Fundamentals · Topic 6 of 13
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Doping
Adding trace impurities to control a semiconductor's carrier type and concentration.
What you’ll learn
- What doping does
- Donors vs acceptors
- How doping level sets conductivity
Why it matters
Doping is the single most important tool for turning inert silicon into working devices.
Explanation
Doping introduces small, controlled amounts of impurity atoms into the lattice. Donor atoms (e.g. phosphorus) add extra electrons; acceptor atoms (e.g. boron) add holes. Even parts-per-million doping changes conductivity by orders of magnitude.
By choosing the dopant and its concentration, engineers set whether a region is electron-rich (n-type) or hole-rich (p-type), and how strongly it conducts.
Visual explanation
Key terminology
- Dopant
- An impurity added to change carrier concentration.
- Donor
- A dopant that donates a free electron (n-type).
- Acceptor
- A dopant that accepts an electron, creating a hole (p-type).
Example
Common mistakes
Watch out for:
- Assuming more doping is always better — heavy doping raises leakage and can degrade mobility.
- Mixing up donors (n-type) and acceptors (p-type).
Real-world application
Ion implantation places precise dopant doses exactly where transistors need them.
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