Lecture6(3)

Current electron or hole flow is dependent on the

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Unformatted text preview: rent (electron or hole flow) is dependent on the concentration of electrons and holes in the material. – It is useful to relate the carrier concentration to average energy (Fermi energy) in the material. •  How to calculate carrier concentration Between E~(E+dE), the number of electron is given by dn = f(E) × gc(E) dE n0 = ∫ ' Ec Ec f ( E ) × gc ( E ) dE EE 332 Spring 2013 Density Density of States Concept of States EE 332 Spring 2013 DensityDensity of State Concept of States EE 332 Spring 2013 Probability of Occupation Concept Probability of Occupation EE 332 Spring 2013 Fermi Function and Carrier Concentration Fermi Function and Carrier Concentration EE 332 Spring 2013 C Carrier Concentration Chargeharge Carrier Concentration EE 332 Spring 2013 Electron and Hole Concentration Electron and Hole Concentration EE 332 Spring 2013 Electron Distribution in Solids - Fermi-Dirac Statistics Maxwell-Boltzmann Approximation If E-Ef >> kT, exp( E − EF ) >> 1 kT E − EF E − EF 1+ exp( ) ≈ exp( ) kT kT E − EF E E fB ( E ) = exp( − ) = exp( F ) exp( − ) kT kT kT E = A exp( − ) kT E For hole where A = exp( F ) kT The probability the energy state E is occupied by an electron is give by fB(E) EF E ) exp( ) kT kT E = B exp( ) kT E where B = exp( − F ) kT 1− f ( E ) = exp( − EE 332 Spring 2013 Equilibrium Electron Concentration Equilibrium Electron Concentration EE 332 Spring 2013 Concentration of Electrons n= ∫ ∞ Ec gc ( E ) exp( E − EF )dE kT * 3/ 2 E − EF 1 ( 2mn )...
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This document was uploaded on 02/18/2014.

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