Doping: N-Type and P-Type Semiconductors

Adding impurities on purpose.

Adding a tiny amount of a five-valence element such as phosphorus to silicon gives spare electrons and creates N-type material. Adding a three-valence element such as boron leaves vacancies, called holes, and creates P-type material.

In N-type the majority carriers are electrons and in P-type they are holes. Joining the two forms a PN junction, the heart of diodes, transistors and integrated circuits.

• Donor atoms supply electrons; acceptor atoms accept them.
• Doped material stays electrically neutral overall.
• Doping can change conductivity a million times over.

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