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Unformatted text preview: and Metals (continued) (continued)
Conduction Band Valence Band
Conductor Semiconductor Insulator Hole - Electron Pairs Hole
s s Sometimes thermal energy is enough to cause an electron to Sometimes jump from the valence band to the conduction band jump – produces a hole - electron pair Electrons also “fall” back out of the conduction band into the Electrons valence band, combining with a hole valence pair elimination pair creation hole electron Improving Conduction by Doping Improving
s To make semiconductors better conductors, add impurities To (dopants) to contribute extra electrons or extra holes (dopants) – elements with 5 outer electrons contribute an extra electron to elements the lattice (donor dopant) the – elements with 3 outer electrons accept an electron from the elements silicon (acceptor dopant) silicon s Improving Conduction by Doping (cont.) (cont.) Phosphorus and arsenic are Phosphorus
donor dopants donor – if phosphorus is if introduced into the silicon lattice, there is an extra electron “free” to move around and contribute to electric current electric – produces n type silicon produces silicon » very loosely bound to atom and can easily jump to conduction band » sometimes use + symbol to indicate heavier doping, so n+ silicon – phosph...
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This note was uploaded on 04/04/2010 for the course EE 3 taught by Professor Staff during the Winter '08 term at UCLA.
- Winter '08