Lecture8(9)

G externally applied voltage is applied to a

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Unformatted text preview: 332 Spring 2013 Carrier Drift Carrier Drift •  When an electric field (e.g. externally applied voltage) is applied to a semiconductor, mobile charge carriers will be accelerated by the electrostatic force. This force superimposes on the random motion of electrons: •  Electrons drifts in the direction opposite to the electric field -> Current flows * Because of scattering, electrons in a semiconductor do not achieve constant acceleration. However, they can be viewed as quasi-classical particles moving at a constant average drift velocity vd EE 332 Spring 2013 Electrons as Moving Particles Electrons as Moving Particles EE 332 Spring 2013 Carrier Effective Mass Carrier Mass Carrier Effective Effective Mass In an electric field, E, an electron or a hole accelerates: EE 332 Spring 2013 Electron Path in a Semiconductor Electron Path a a Semiconductor Electron Path inin Semiconductor Between collisions, carriers accelerate in the direction of field EE 332 Spring 2013 Electron Momentum Electron Momentum Electron Momentum •  With every collision the electron loses momentum •  Between collisions, the electron gains momentum EE 332 Spring 2013 C Carrier Mobilityarrier Mobility EE 332 Spring 2013 Carrier Mobility in Semiconductor Carrier Mobility in Semiconductor EE 332 Spring 2013 Electron and and Mobility Mobility of ElectronHole Hole EE 332 Spring 2013 Electron and Hole Drift in Electric Field Electron and Hole Drift in Electric Field EE 332 Spring 2013 D Drift Current rift Current EE 332 Spring 2013 Conduction Process n-Type...
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