Semiconductor Device Fundamentals, 1st Edt. by Robert f. Pierret - Solution Manuel Copy
Mobile Carrier Action Reading Assignment Pierret : Chap 2 and Chap 3 Instructor: Prof. Dr. Ir. Djoko...
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Transcript of Mobile Carrier Action Reading Assignment Pierret : Chap 2 and Chap 3 Instructor: Prof. Dr. Ir. Djoko...
Mobile Carrier ActionReading Assignment
Pierret : Chap 2 and Chap 3
InstructorInstructor : Prof. Dr. Ir. Djoko Hartanto, M.Sc.: Prof. Dr. Ir. Djoko Hartanto, M.Sc.: Arief Udhiarto, S.T, M.T: Arief Udhiarto, S.T, M.T
SourceSource :: Professor Nathan Cheung, U.C. Berkeley
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Carrier Concentration vs Carrier Concentration vs TemperatureTemperature
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Dependence of EDependence of Eff on on TemperatureTemperature
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Degenerate Semiconductors
If dopant concentrations are very high such that EF is < 3kT from EC or EV, we have to to use the full Fermi-Dirac probability function
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Electron as Moving ParticleElectron as Moving Particle
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Semiconductor Carriers Effective Semiconductor Carriers Effective MassMass
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Carrier ScatteringCarrier Scattering
Because of scattering, mobile cariers in a semiconductor do not achieve constant acceleration. However, they can be viewed as classical particles moving at a constant average drift velocity
1) “Lattice Vibration (phonons) scattering”-No dopant dependence-Increases with increasing temperature
2) Ionized impurity scattering-Increases with NA +ND (total dopant conc)-Decreases with increasing temperature
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Carrier Drift
With an electric field, mobile charge-carriers will be accelerated by the electrostatic force. This force superimposes on the random thermal motion of electrons:
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The average current in any direction is zero, if no electric field is applied
Electrons drift in the direction opposite to the E – field Current flows
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Electron MomentumElectron Momentum
With every collision, the electron loses With every collision, the electron loses momentum momentum
Between collision, the electron gains Between collision, the electron gains momentum momentum
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Balancing momentum gain and momentum lost
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Mobility Dependence on Mobility Dependence on DopingDoping
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Electrical Conductivity σ
When an electric field is applied, current flows due to drift of mobile electrons and holes:
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Electrical Resistivity ρ
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Electrical Resistance
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Example
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Example (continued)
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Temperature Effect on Mobility
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Example: Temperature Example: Temperature Dependence of Dependence of ρρ
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Diffusion CurrentDiffusion Current
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Diffusion Current Density ( Fick’s First Law)
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Total Current Density