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Unformatted text preview: e are 2 scattering mechanisms
Recall
• Lattice Scattering
• Impurity Scattering – Lattice scattering is a result of temp dependent lattice
Lattice
vibrations and increase with increasing temperature.
Thus lattice scattering dominates at high temperatures
Thus
– Impurity scattering is scattering from dopant atoms. and
Impurity
is not generally temperature sensitive. Heavy doping
decreases mobility.
decreases
– Mobility goes as T3/2 for low temps and T3/2 at high
temps.
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 Efield Effects in Semiconductors Saturation of electron drift velocity at high electric fields for Si. The Hall Effect
The
• Situation
– 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
The
the width
the
– A resulting Ey is set up (see above) as a result of
charge separation
charge The Hall Effect
The
– The charge shift will occur until Ey = vxBz and no
more.
more.
– At this point the force on the e...
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This note was uploaded on 04/02/2014 for the course EECS 321 taught by Professor Zorman during the Spring '10 term at Case Western.
 Spring '10
 ZORMAN

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