ECE 3150
Spring 2009
Week 3 Recitation
Ask for Homework questions first on Homework 2 (you can choose to do Work problems
below first)
Additional Work problems:
1.
For a piece of semiconductor under equilibrium at room temperature which contains
N
A
=10
17
cm
3
and
N
D
=10
15
cm
3
, what is the best estimate for the electron concentration,
assuming
n
i
= 10
10
cm
3
and complete ionization of dopants? (Teach ways to estimate
without using a calculator)
(a) 10
3
cm
3
(b) 10
10
cm
3
(c) 10
15
cm
3
(d) 9.9
×
10
16
cm
3
(e) 10
17
cm
3
2.
Same semiconductor from Question 2, what is the hole concentration?
3.
Same semiconductor as Prob. 2. If we apply an electric field, what will be the species
that will contribute most to the electric current?
4.
Same from Prob. 2, what is the electrostatic potential at equilibrium?
Is it negative or
positive?
Draw the band diagram as a graphical method.
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 Spring '07
 SPENCER
 Equilibrium, Semiconductors, Microelectronics, Pn junction

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