Unformatted text preview: MatE 153: HW 5: Due Wed 11/9/11 • •
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• Homework must be submitted on the due date by the start of class period. Homework will
be accepted during the class period but your grade will be reduced by 10%. After the end of
the class period, no homework will be accepted unless you have a verifiable, legitimate
reason.
Write your name very clearly on the upper right corner of the first page of your
assignment.
You may work with up to 3 other students. List students you worked with. Be sure to
clearly separate their names from yours. You must submit your own set of solutions.
You will receive a 0 and be reported to the University if you submit any solution or partial
solution you did not actively participate in creating and fully understand (see the Greensheet
for more specific information).
You will see this material (though not the same or similar questions) on the midterm and
final. If you can’t do it now come see me! Reading Kasap: 5.2 and 5.3 Be sure to look over the reading review notes on D2L. This
will help you prepare for the final. Total Points: 70 Points 1. How would the saturation temperature change if you increased the dopant concentration?
if you decreased the band gap? (5 points)
2. What is a degenerate semiconductor? What would be a use of such a semiconductor? (5
points)
3. Si is doped with 1018 atoms/cm3 of B.
a. Using a spreadsheet program, plot the ln p versus T for 0 to 2000K. For full
credit, clearly indicate the equation you used in each region. (10 points)
b. What is TI? (5 points)
c. What is TS? (5 points)
d. What is the conductivity at 300K? (5 points)
e. Calculate the height of the Fermi energy at 300K. (5 points)
4. A Si wafer has been doped ntype with 1017 As atoms cm3. Be sure to consider the
temperaturedependence of the mobility in the questions below.
a. Calculate the conductivity of the sample at 27 °C. (5 points)
b. Calculate the conductivity of the sample at at 127 °C. (5 points)
c. Calculate the conductivity of the sample at 60 °C. (5 points)
Suppose our Si wafer has been doped with both 5 x 1016 B atoms cm3 and 1017 As atoms cm3.
d. Is this sample ntype or ptype at 27 °C? Calculate the conductivity at 27 °C. (5 points)
e. What is the Fermi energy of this sample (5 points)
5. Define the difference between drift and diffusion of carriers in Figure 5.31. (5 points) ...
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 Fall '08
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 Class Period, Fermi

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