Chapter 3 Diodes2 - /2/12 . Chapter 3 Diodes Physical...

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S J T U J. C h e n 1 3/2/12 Physical Operation of Diodes Chapter 3 Diodes
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3/2/12 SJTU J. Chen 2 Doped semiconductor—— n type P Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si + Free E Donor bound charge
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3/2/12 SJTU J. Chen 3 Donor --- pentavalent impurity provides free el ectrons (usually entirely ionized at room temp erature) Positive bound charge ---impurity atom donatin g electron gives rise to positive bound charge Majority carriers - -- free electrons (mostly gener ated by ionized donor and a very tiny portion b y thermal ionization) . Minority carriers - -- holes (only generated by th ermal ionization) . n type semiconductor
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3/2/12 SJTU J. Chen 4 Thermal equilibrium equation Electric neutral equation Carrier concentration for n type where ND is the donor concentration 2 0 0 i n n n p n = D n n N p n + = 0 0
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3/2/12 SJTU J. Chen 5 Carrier concentration for n type In a n type Si, the following relationships hold (at r oom temperature): and 0 0 0 0 n i n n n i n n p n p n + 0 2 0 / n D n i D n N p n N
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3/2/12 SJTU J. Chen 6 Doped semiconductor—— p type Al Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si - Hole Acceptor bound charge
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3/2/12 SJTU J. Chen 7 Acceptor --- trivalent impurity provides holes (usually e ntirely ionized) Negative bound charge --- impurity atom accepting ho le give rise to negative bound charge Majority carriers- -- holes (mostly generated by ionized acceptor and a tiny small portion by thermal ionizatio n) Minority carriers- -- free electrons (only generated by t hermal ionization.) p type semiconductor
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3/2/12 SJTU J. Chen 8 Thermal equilibrium equation Electric neutral equation Carrier concentration for p type where NA is the acceptor concentration 2 0 0 p p i p n n × = 0 0 p p A p n N = +
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3/2/12 SJTU J. Chen 9 Carrier concentration for p type In a p type Si, the following relationships hold (at room temperature): and 0 0 0 0 p i p p p i p n n p n n + 0 2 0 / p A p i A p N n n N 2245 2245
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This note was uploaded on 03/02/2012 for the course EI 207 taught by Professor Chengjianping during the Fall '10 term at Shanghai Jiao Tong University.

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Chapter 3 Diodes2 - /2/12 . Chapter 3 Diodes Physical...

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