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Unformatted text preview: 1 Semiconductors Intrinsic Si Si Si Si Si Si Si Si Si Si Si Si e e e e C E V E h h h h i n Nmaterial Si Si Si Si Si P Si Si Si e e e e C E V E donor E with minimum thermal energy this becomes a free electron D N density of Donor atoms like P . Available free electron (N negative) material is still neutral since ve charged electron cancels positively charged P ion. Pmaterial Si Si Si Si Si In Si Si Si Si Si Si h h h h C E V E with minimum thermal energy an electron can be absorbed to this bond (p positive) material is still neutral. a E cceptor A N density of acceptor atoms like In . 2 D N n = in an Nmaterial A N p = in an Pmaterial Turns out that the density of the other carries goes down i.e. in Nmaterial: = = D i D N n p N n 2 Density of free electrons or holes of an intrinsic semiconductor i n In Pmaterial: = = A i A N n n N p 2 i n = depends on how much thermal energy is available (Temperature dependent) at 27C (300K)...
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 Fall '10
 Mohammadi

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