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Unformatted text preview: nority carriers s be neglecte ed? Why can the contribution of min What is the overall charge state of the samplle? Positive, n negative, or n neutral? Chap pter 5 – page 4 4 Invarianc ce of Fermi level Practical devi ices consist o of different materials, d opants, dop ping concent trations, etc. . At equilibrium A m there is no o net curren nt flow ermi level is s constant ac cross differe ent regions, that is: Fe dEF dE 0 dx Proof P Assume two r A regions (1) a and (2) Region (1): Fermi‐Dira ac distributio 1(E) on f Density of f states ρ1(E) ) Region (2): Fermi‐Dira ac distributio 2(E) on f Density of f states ρ2(E) ) f1 E f 2 E EF EF2 F1 Current t from (1) to ( (2) = Curren nt from (2) to o (1) Chap pter 5 – page 5 5 At the energy E, the rate of transfer from a first region to a second region is proportional to the number of filled states in the first region and also to the number of empty states in the second region. Rate from (1) to (2) 1 E f1 E 2 E 1 f 2 E Rate from (2) to (1) 2 E f 2 E 1 E 1 f1 E Both rates are equal. Multiplying out yields: 1 f1 2 1 f1 2 f 2 cancels 2 f 2 1 2 f 2 1 f1 cancels Thus it follows that and f1 f 2 E F1 E F 2 Chapter 5 – page 6...
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This note was uploaded on 04/03/2014 for the course ECSE 2210 taught by Professor Huang during the Fall '12 term at Rensselaer Polytechnic Institute.

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