1. In any electrically conductive substance, what are charge carriers? Identify the charge carriers in metallic substances, semiconducting substances, and conductive liquids.
2.Engineers and scientists often use energy band diagrams to graphically illustrate the energy levels of electrons in different substances. Electrons are shown as solid dots:
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Based on these diagrams, answer the following questions:
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- Which type of material is the best conductor of electricity, and why?
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- Which type of material is the worst conductor of electricity, and why?
3. Describe the difference between an intrinsic and an extrinsic semiconducting substance.
4. What effect does doping concentration have on the electrical conductivity of an extrinsic semiconductor?
5. What must be done to an intrinsic semiconductor to turn it into an "N-type" semiconductor?
6. What must be done to an intrinsic semiconductor to turn it into a "P-type" semiconductor?
7. When "P" and "N" type semiconductor pieces are brought into close contact, free electrons from the "N" piece will rush over to fill holes in the "P" piece, creating a zone on both sides of the contact region devoid of charge carriers. What is this zone called, and what are its electrical characteristics?
8. What happens to the thickness of the depletion region in a PN junction when an external voltage is applied to it?
9.
Insert a diode into this circuit schematic in the correct direction to make it forward-biased by the battery voltage:
10. If a semiconductor PN junction is reverse-biased, ideally no continuous current will go through it. However, in real life there will be a small amount of reverse-bias current that goes through the junction. How is this possible? What allows this reverse current to flow?
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