Download Exam 3 Solutions - Hardware Competition EEL | EEL 4937 and more Exams Electrical and Electronics Engineering in PDF only on Docsity! EEL 4937-001 ELECTRONIC MATERIALS Spring. 2001
EXAM OI Wednesday; April 25, 2001
NAME: COLUT / OKLL SS#:
GENERAL RULES:
This is a CLOSED BOOK, CLOSED NOTES test.
You are allowed to use an 8 1/2 x 11" SHEET with whatever information you find useful
Show ALL YOUR WORK on the test.
For PARTIAL CREDIT you must clearly show ALL INTERMEDIATE STEPS. PLAIN
ANSWERS WILL GET NO CREDIT.
You MUST include UNITS with your answers for FULL credit.
TOTAL POINTS: 100
GOOD LUC K Ut
on i
Problem #1 (LOpts): A thermocouple is made from Chromel and. Alumel wires. The
difference of the Seebeck coefficients S of Alumel and Chromel is 40 zV/K. What
thermovoltage is measured if one of the Chromel/Alumel contacts is inserted in ice-water
(273.16 K) and the other is held at 1000 K?
Vag J (5, -S,)4T
'o
- .
( bG,%T
. {One
tooo K ’ y
2 Mea lt + wal -T |
233.16
PICK
- 4O [1900 - 2911] AV
= 14033.6 wl ~ 24. OF HV
Problem #4: (10 pts) A n-type silicon wafer has been doped with 10" cm? As atoms. The
intrinsic carrier concentration of Si is 1.45x10" cm?,
a) Assuming total ionization of the As atoms, what. is.the electron density in the
conduction band? (3. pts)
b) Calculate the position of the Fermi energy of the doped wafer with respect to the
position of the Fermi energy of intrinsic Si.(7 pts)
4) As 10? cee?
L) Ep ~ Eee kT tu Na
Problem #5 (15 pts): The Fermi energy of an n-type semiconductor is 0.1 eV below its
conduction band.
a) What is the probability to find an electron in’a state at the bottom of the conduction
band? (8 pts)
b) What is the dopant density of the semiconductor? (7 pts)
|
{(o.el)= 20.001 => 2%
| + exp ( Saew)
5)
AY =u, exp | “EyFe |
VU; Was cot Glen...
=s fall ple fov selves 4)
Problem #6: (15 pts) Draw a schematic “log vs. (1/T)" diagram of the temperature
dependence of
a) carrier density (5 pts)
b) mobility (5 pts)
c) conductivity (5 pts)
of an extrinsic semiconductor
hn
