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Unformatted text preview: lectrons in the y
At
direction will equal zero and no deflection of the
current will occur.
current
– Electrodes at either side of the SC can be used to
Electrodes
measure the voltage resulting from Ey otherwise
measure
known as the Hall voltage.
known
– The text derives an expression for the Hall
The
coefficient, which is the inverse of the hole
concentration times the charge.
concentration The Hall Effect The Hall effect  graphically The Fermi Level at Equilibrium
The
• General Rule: No discontinuities or gradients can
General
exist in the equilibrium Fermi Level.
exist
• Illustration
– Two different materials in intimate contact
• No external fields or thermal gradients so no net charge flow – As such energy is conserved, so electrons moving from
As
one material to the other are countered with equivalent
electrons going the other way (charge balance)
electrons
– Analysis of filled and empty states in each material
Analysis
using FermiDirac statistics will show that (with a bit of
algebra) f(E1) = f(E2).
algebra)
).
– Recall that a filled state is represented by f(E) and thus an empty
Recall
state by 1 f(E).
state – This requires that EF1 = EF2 The Fermi Level at Equilibrium Two materials in intimate contact at equilibrium. Since the
net motion of electrons is zero, the equilibrium Fermi level
must be constant throughout....
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 Spring '10
 ZORMAN

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