Unformatted text preview: e are 2 scattering mechanisms
• Lattice Scattering
• Impurity Scattering – Lattice scattering is a result of temp dependent lattice
vibrations and increase with increasing temperature.
Thus lattice scattering dominates at high temperatures
– Impurity scattering is scattering from dopant atoms. and
is not generally temperature sensitive. Heavy doping
– Mobility goes as T3/2 for low temps and T-3/2 at high
temps. Mobility and Dopant Concentration Variation of mobility with total doping impurity
concentration (Na + Nd ) for Ge, Si, and GaAs at 300 K. Mobility and Temperature Approximate temperature dependence of mobility
with both lattice and impurity scattering. High E-field Effects in Semiconductors Saturation of electron drift velocity at high electric fields for Si. The Hall Effect
– Current flow in a SC is along the “long” axis
– B field directed orthogonal to current flow • Governing equations:
– F = q(E + v x B)
Solving yields Fy = q(Ey – vxBz)
Physically Fy = 0, so Ey = vxBz • Why Fy = 0?
– The B field causes holes in the SC to shift along
– A resulting Ey is set up (see above) as a result of
charge The Hall Effect
– The charge shift will occur until Ey = vxBz and no
– At this point the force on the e...
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- Spring '10
- Electrons, Carrier Concentrations, E Fields, Lattice Scattering