1. "Charge carriers" are any particles possessing an electrical charge, whose coordinated motion through a substance constitutes an electric current. Different types of substances have different charge carriers:
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Metals: "free" (conduction-band) electrons
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Semiconductors: electrons and holes
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Liquids: ions
2. Metals are the best conductors of electricity, because many of their electrons occupy the "conduction band" at normal temperatures.
Insulators are the worst conductors of electricity, because a tremendous amount of energy must be invested before an electron can "leap" across the large gap into the conduction band.
3. An ïntrinsic" semiconducting material is absolutely pure. An ëxtrinsic" semiconducting material has dopant(s) added for enhanced conductivity.
4. The more concentrated the "doping," the greater the conductivity of the material.
5. A pentavalent dopant must be added to it, to create donor electrons.
6. A trivalent dopant must be added to it, to create acceptor holes.
7. This is called the depletion region, and it is essentially an insulator at room temperatures.
8. The answer to this question depends entirely on the polarity of the applied voltage! One polarity tends to expand the depletion region, while the opposite polarity tends to compress it. I'll let you determine which polarity performs which action, based on your research.
9. Ask me in class.
10. Minority carriers allow reverse current through a PN junction.
