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Homework #3, Due Thursday 10/1/09
I.
(20 points) Calculated the magnitude of the velocity of an electron in GaAs with
energy of 3/2
k
B
T above
the conduction band edge (the thermal average energy)
with T = 300K, assuming the validity of the effective mass approximation.
Repeat for Si, treating the system as isotropic (not directionally dependent) using
the conductivity, effective mass.
(This actually works.)
In each case, put your
answers in units of m/s = nm/ns (relevant for current device scales and clock
frequencies) and km/hour (relevant to everyday experience).
Appendix III may
be helpful.
Note that the conductivity effective masses are provided in Example
36 of the text, or could be calculated for Si as done in the example.
(Also, just
FYI for now, note that the average velocity of charge carriers through
conventional transistors now approaches this velocity.)
II.
(20 points) Consider conductionband minimum energy valleys centered at the X
points, and assume that for the valley centered at the X point along the (100)
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 Fall '08
 Banjeree

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